Center Filter Homebrew Ideas
Related Local Links:
Filters FAQ and Links pages
Center filters can cost an amazing $2,850 US$ (for Super Angulon
210mm f/8). So many of us have an interest in possible solutions we can do for less. In
some cases, center filter use may be optional, depending on your choice of subject and
technique. Modern digital filtering and image merging (multiple exposures at different
stops on tripod..) may make it possible to achieve more uniform effects with less effort.
Finally, some photographers have had success with making their own low cost center filters,
with their tips available to you below.
Related Postings
Date: Tue, 11 Jan 2000
From: "Alexander Kraus" alex_kraus@sprynet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Making a center filter...
Todd E. Maurer maurert@apk.net wrote
> When researching the Metrogon that Mr. Grimes' WEB put me onto, I got to
> see pictures of that lens' center filters. These seemed to simply have
> an asterisk pattern of metal foil in the center. I couldn't tell if the
> foil was opaque or semitransparent.
>
> Anyone ever try making their own center filter by just putting an foil
> asterisk on a clear filter? Seems like too simple a solution... Not
> near as elegant as a neutral density filter that gradually gets darker
> in the center. But it seemd like it might actually work. I'd expect it
> to be sensitive to the aperture setting. But hey for the cost difference
> between a UV and a "real" center filter, I could make a filter (even
> from multi coated glass filters for every marked aperture and still
> save a bundle.
>
> Todd
Well, I'd bet this would really diminish the performance of the
lens. First
of all you would need a foil that is
a) perfectly neutral grey,
b) perfectly planparallel (equally thick everywhere) and
c) optically homogeneous.
Secondly you need to glue it to the glass. Again you need a perfect
crystall clear glue and you have to apply it equally thick everywhere to
avoid bumps. After all you don't want to copy a Zeiss Softar ;-) The foil
has to be semitransparent. Since the depth of field of a wide angle lens
is very large, an opaque foil would cause a black spot in the center of
your image. I think these prerequisites cannot be fulfilled without very
sophisticated equipments/materials.
You might try an other approach. Take a (cheap) UV-Filter, cut a
star-shaped mask out of cardboard and place it a couple of millimeters
above the glass surface. Then spray a *very fine* mist of flat black paint
through the mask towards the glass. Let the distance between can and glass
be at least 2 feet in order to avoid getting an completely opaque black
spot.
I have never tried this procedure my self and I have never heard that
another one did it before, but I think it might actually work.
If it fails - just clean the filter with some methylene chloride or
acetone and you haven't lost anything. If you try it, don't forget to post
how it works! :-)
Alex
From: Bill Peters bill.peters@home.com
Date: Thu, 13 Jan 2000
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Making a center filter...
Todd,
Metrogon Centre Filters are available from the Surplus Shed in red and
yellow for a few dollars each. These are the evaporated metal type. The
ones I got had some minor surface damage and fungus spots - more cosmetic
than anything that would degrade performance. They are so inexpensive you
might order two or three and cherry pick.
Now if you want to shoot color :-\
http://www.surplusshed.com/filters.html
cheers,
Bill Peters
Date: Fri, 14 Jan 2000
From: Harald Finster finster@ave.ac.agit.de
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Center Filter? who uses, comments please
Hi Rodney, hi all,
mr_vince@hotmail.com wrote:
> I've seen them for sale for extreme wide angle lenses. I am curious
> if they are necessary?
The answer depends on your application.
You WILL need a center filter, if you are going to photograph
evenly illumuinated objects. If you are working on B&W;, you
can compensate the light falloff in your darkroom - that's the
poor man's solution :-)
In same cases, e.g. in landscape photography, the light falloff
might even be useful. If you shift your lens up, the falloff
'replaces' the graduated neutral density filter.
> I have a 90mm Nikkor f8 and I guess it doesn't need a filter, because
> I have noticed no light fall-off in my transparencies.
I had some experience with a 47mm lens, which definately REQUIRED
the filter. But a 90mm might be ok without one.
Harald
Date: Thu, 13 Jan 2000
From: "M. Denis Hill" denis@area360.com
To: panorama-l@sci.monash.edu.au
Subject: RE: Fuji G617 focusing screens, ND filter usage, etc., questions
In my experience, the center filter becomes optional when:
a) The subject does not contain large areas of even tones extending into
the
corners (e.g., sky), or
b) The lens is stopped down to f22 or beyond, or
c) A combination of "a" and "b."
I've heard one prominent IAPP member claim that she never uses a center
filter on a Fuji, just stops way down.
IMO, it is preferable to get the image as right as possible in the camera.
BTW, stacking a standard filter behind the center filter (in my case, a
Heliopan) caused severe vignetting at nominal apertures.
The correct way to frame an image with the G617 is to line things up so
you see the level in the notch at the bottom of the viewfinder frame. In
my experience, I often found this gave accurate framing on the vertical
axis, but I usually got extra image on the horizontal axis. Although I
never used one with the G617 I owned, I think a ground glass would be a
very useful accessory unless you want to frame with fudge factor.
As I recall, using a cable release on the lens did not tell the winding
mechanism an exposure had been made.
The Fuji is a real workhorse. Enjoy it! And don't forget that it takes
vertical pictures, too.
M. Denis Hill
Area 360 Communications
http://www.area360.com
Date: Tue, 11 Jan 2000
From: "Alexander Kraus" alex_kraus@sprynet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Making a center filter...
Todd E. Maurer maurert@apk.net wrote
> When researching the Metrogon that Mr. Grimes' WEB put me onto, I got to
> see pictures of that lens' center filters. These seemed to simply have
> an asterisk pattern of metal foil in the center. I couldn't tell if the
> foil was opaque or semitransparent.
>
> Anyone ever try making their own center filter by just putting an foil
> asterisk on a clear filter? Seems like too simple a solution... Not
> near as elegant as a neutral density filter that gradually gets darker
> in the center. But it seemd like it might actually work. I'd expect it
> to be sensitive to the aperture setting. But hey for the cost difference
> between a UV and a "real" center filter, I could make a filter (even
> from multi coated glass filters for every marked aperture and still
> save a bundle.
>
> Todd
Well, I'd bet this would really diminish the performance of the lens.
First of all you would need a foil that is
a) perfectly neutral grey,
b) perfectly planparallel (equally thick everywhere) and
c) optically homogeneous.
Secondly you need to glue it to the glass. Again you need a
perfect crystall clear glue and you have to apply it equally thick
everywhere to avoid bumps. After all you don't want to copy a Zeiss Softar
;-) The foil has to be semitransparent. Since the depth of field of a wide
angle lens is very large, an opaque foil would cause a black spot in the
center of your image. I think these prerequisites cannot be fulfilled
without very sophisticated equipments/materials.
You might try an other approach. Take a (cheap) UV-Filter, cut a
star-shaped mask out of cardboard and place it a couple of millimeters
above the glass surface. Then spray a *very fine* mist of flat black paint
through the mask towards the glass. Let the distance between can and glass
be at least 2 feet in order to avoid getting an completely opaque black
spot. I have never tried this procedure my self and I have never heard
that anothe r one did it before, but I think it might actually work. If it
fails - just clean the filter with some methylene chloride or acetone and
you haven't lost anything.
If you try it, don't forget to post how it works! :-)
Alex
Date: Tue, 11 Jan 2000
From: "Todd E. Maurer" maurert@apk.net
Newsgroups: rec.photo.equipment.large-format
Subject: Making a center filter...
When researching the Metrogon that Mr. Grimes' WEB put me onto, I got to
see pictures of that lens' center filters. These seemed to simply have
an asterisk pattern of metal foil in the center. I couldn't tell if the
foil was opaque or semitransparent.
Anyone ever try making their own center filter by just putting an foil
asterisk on a clear filter? Seems like too simple a solution... Not
near as elegant as a neutral density filter that gradually gets darker
in the center. But it seemd like it might actually work. I'd expect it
to be sensitive to the aperture setting. But hey for the cost difference
between a UV and a "real" center filter, I could make a filter (even
from multi coated glass filters for every marked aperture and still
save a bundle.
Todd
From Panoramic Mailing List:
Date: Sun, 19 Dec 1999
From: Joel Seaman jseaman@taconic.net
Subject: Re: Horseman 612
John,
Some folks allegedly are successful with the 45MM. They seem to get by
with the help of a Schnieder Center filter which is a 2 stop (4X)
filter, and substantially less expensive. I did have occasional images
that worked well with the 45MM, but this was extremely inconsistent.
Rodenstock recommeds a 1 1/2 stop for both lenses. The Rodenstock 1 1/2
stop (ND 0.45) is the same as the Heliopan which you might find for less
money. I have the ND 0.45 Rodenstock but since they are "hand made"
they vary in actual compensation, and therefore my 1 2/3 stop Velvia /
100VS solution. You will have to test yours to see what it really
needs. Rodenstock told me that the ND 0.45 should require only 1 1/3
stop compensation.....fat chance.
When I bought my Horseman Samy's Camera had the best price which was
their 612 kits, although, other then giving Samy's my credit card # and
receiving the camera, I found them to be less than useless and less than
helpful.
Good luck
Joel
From: "Todd E. Maurer" maurert@apk.net
Newsgroups: rec.photo.equipment.large-format
Date: Thu, 27 Jul 2000
Subject: Re: f/8 vs. f/5.6 65mm Super Angulon
The center filter might help even things out.
I just got mine for my 65 mm F8. Haven't have time
for even a test shot! The less expensive Heliopan
was hard to come by as they are discontinued. Around
$200+-20 if you can find it in stock. The Schneider one
is available but a special order item. I was quoted $310
to $500 depending on the dealer.
I won't count on much if any movement. The previous
owner had this lens mounted off center on its board for
shooting architecture with roll film. I found I had to
drop the standard to prevent the worse of the vingetting.
BTW Schneider's web site does not recommend this lens
for 4x5.
Todd
Alan & Juliet Duncanson wrote:
> I am looking for a 65 mm lens to use with 6x9
> and 4x5 formats. I am attracted to the f/8
> Super Angulon in part because of the low price
> for which they are sometimes available.
>
> It appears that, at 100 deg. coverage, the f/8
> will just barely cover 4x5 with no movements.
> Will a center filter help, and maybe allow it
> to cover 2 cm of shift?
>
> Does the f/8 suffer in terms of sharpness in
> comparison? I will be making about 5x
> enlargements.
>
> Thanks - Alan
From Panoramic Mailing List:
Date: Wed, 02 Aug 2000
From: Michel Dusariez dusariez@skynet.be
To: panorama-l@sci.monash.edu.au
Subject: Graduated Filters
Dear panoramist,
I remember to all of you that I am a retail optician in Brussels, Belgium.
About graduated filters, you have to know that it's very easy to made some
yourself.
In any rx spectacles glass factory, who made glass (mineral and organic -
plastic ) for retail opticians, they made any coloration on organic
eyeglass, they put the plastic glass in some tinting liquid at 90-95
centigrade temperature for a few minutes.
The tinting powder come in different hues as well neutral gray and is
very
inexpensive, you can color a lot of glass in one liter of liquid.
The coloration is darker as the glass stay more in the liquid.
They made easily graduate by immersing more or less some part of the
plastic sheet.
With some training it is maybe possible to made some central dark spot.
I hope to have give all off you some usefull informations.
Michel DUSARIEZ.
PS : The last edition of the book " 360o PANOPTIC PHOTOGRAPHY EXPERIMENTS"
is nearly all sold, last copies are always available, persons interrested
can ask more info by E-mail.
>Ya, sure, Peter, I use graduated filters on that thing a lot. And boy, oh
>boy, they have really made a difference; several photos in my new book
>involved the Fuji 617 with 2 or 3 stop ND graduated filters. I use the
>Tiffen Glass ones; they cost about $125 each a few years ago. They're
>rectangular, so one can slide them up and down without getting the edge of
>the filter in the frame. This does limit their use when doing verticals,
>though, because the filter only barely fits inside the "roll bar" and so the
>horizon of dark and light is stuck in the center then. But hey, it works.
>Some of those verticals need a little cropping anyway. The nice thing about
>glass is that it's a lot harder to scratch than resin is. Also, these are a
>nice neutral gray compared to some of the green or amber "grey" that I've
>seen on the market.
>
>Liz Hymans
>
>In a message dated 8/1/00 6:38:13 AM Pacific Daylight Time,
>petermiller@yankeeimage.com writes:
>
> I find the need for graduated filters for the Fuji GX 617.
Michel DUSARIEZ
UNLIMITED FIELDS RESEARCH PANOPTIC IMAGING
KITE AERIAL PHOTOGRAPHY WORDWIDE ASSOCIATION - FOUNDATION
14, Avenue Capitaine PIRET
B-1150 BRUXELLES - BELGIUM
Fax 32 2 512 68 29
From Panoramic Mailing List:
Date: Sun, 20 Aug 2000
From: "rof@mac.com" rof@mac.com
Subject: Re: Linhof 6x17 filter question
as the manufacurer of 612 shift cameras i have found the centerfilters
very
a great deal no matter what the annouonced factor is. Probably 3x (1 1/2
stops) is a good starting point. if you are shooting transparencies you do
not want to overexpose of course, on contrary with color negs i expose for
the far corners if i want an even result which i get by printing in the
center w/o image damage. to deterning the filter factor I take a good spot
meter 1 degree best, read the center and then the clear edge holding
filter
in same position with a light wall as background.ralph
> From: Denton Taylor denton@asan.com
> Reply-To: panorama-l@sci.monash.edu.au
> Date: Sat, 19 Aug 2000
> To: panorama-l@sci.monash.edu.au
>
> Hi all...
>
> I'm the very fortunate owner of a Technorama 6x17 with fixed 90 SA...
>
> I also got the graduated center filter, which, after a roll of chromes
> without it, has made it clear that I need it all the time :-)
>
> But, does anyone know what the filter factor is? Bracketing 6x17 gets
> expensive :-)
Date: Fri, 13 Oct 2000
From: C. Downs
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Centering Filters: Required When?
Paul Mozell
webmaster@amcboston.org wrote:
>These babies are expensive. Which focal lengths make the best use of
>them? Please tell me I won't need one for 75mm!
For many applications you might be able to avoid using one for 75mm on
4x5 film.
I believe that David Muench leaves the filter off for most shots. He
is probably the best known photographer that specializes in this
particular lens. His main film for color is Velvia so it's possible
to not use it even with contrasty films.
My favorite lens for 4x5 wide
angle is the 58XL and unless I'm shooting something that has to be
even from edge to edge like a blank wall used for commercial
advertizing the center filter is not used. This applies mainly to
nature images and will not apply for some types of commercial work
where the background is to be exactly the same from corner to corner
but for most other work even commercial no filter is needed for the
75mm. Actually the light fall off for nature work works very well to
give a slight darkening at the corners that many achieve by burning
and dodging.
You might want to check out one of the many books that
David Muench has out and see if the slight darkening doesn't seem to
work well. In B&W; if you are aware of the slight light loss at the
edges you can increase the exposure just a bit and dodge the center
when printing. Again the effect is not that distracting and sometimes
works really well. DO be careful if you use a polarizing filter with
the wide angles as they will sometimes give very uneven skies. This
happens due to the angle of light coming from one side of the sky is
partly polarized and on the other end of the image the angle is too
far off of the polarizing axis to work as well.
I certainly would try
the lens for a while without the center filter and see if you can live
without it. It is a pain to use as it is easily scratched and as you
said expensive to replace. It adds another couple of surfaces to flair
and you do loose light. One of the strange things I have noticed is
that the same formula lens on an 8x10 camera { around 150mm} is not
usually questioned as to the need for the center filter and the light
fall off is the same. If you have access to any of the books in the
"Images of Wildness" series look for George Humphries work and you
will see the majority of images are shot on 4x5 with the
75mm.....never a center filter used.!
As I said try it with out the filter and for most things I think you
will be happy.
Date: Fri, 13 Oct 2000
From: p2macgahan@compuserve.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Centering Filters: Required When?
pmozell@world.com wrote:
> These babies are expensive. Which focal lengths make the best use of
> them? Please tell me I won't need one for 75mm!
Whether you feel you need one or not has to do with your taste and how
you use the lens. If you want a quantative answer and you are using a
schneider 75 SA, you might go to their website
(http://www.schneideroptics.com/large/super_angulon/75/daten.html) will
get you directly to the description of the 75 SA. There is an
illumination curve that tells you the percent illumination as a
function of the distance off axis. You can convert % to f:stops (50%
means you need 1 more f:stop). If you want the answer from Rodenstock
you can probably find it in their brochures. If you want it from
Nikon, or Fuji, well you're out of luck, but their lenses should be
similar to Schneider and the illumination fall-off seems to me a little
less. Thus, the Schneider curves are probably a good guide.
If you are troubled by the cost, sometimes a used one is available a
little cheaper. There are both Heliopan and OEM versions. Personally,
I think they are both very good.
Good luck.
From Contax Mailing List:
Date: Thu, 16 Nov 2000
From: Bob Shell bob@bobshell.com
Subject: Re: AW: [CONTAX] Re: Ziess Jena
Also, there were some wide angle lenses which had little propellers
(like on an airplane) on the front. You would spin the propeller just
before taking the photo, and this worked like a graduated neutral
density filter to even out the illumination.
Bob
[Ed. note: handy note, as I have suspected this, but glad to see it
confirmed by an owner/user...]
Date: Mon, 15 Jan 2001
From: Heavysteam@aol.com
To: rmonagha@post.cis.smu.edu
Subject: Crazy prices
I was forced to purchase a graduated center filter for my Hasselblad
Xpan's 45mm lens at a price of $240. Despite what Hassleblad says, the
severe light drop-off in this lens prevents successful use even with print
film with most subjects. This filter should be provided with the lens or
camera kit, but is not. The price is about half of what you pay for the
whole lens. Conversely, I paid less than that for a huge (and beautifully
made) center filter for my LF Schnieder 75mm Super Angulon.
Date: Sat, 13 Jan 2001
From: drdagor@my-deja.com
Newsgroups: rec.photo.equipment.large-format
Subject: How Could You Build A Practical Center Spot Filter?
I've got a couple of older WA lenses with excellent coverage...
I'm also trying to pick up one or two of the modern WA lenses with
incredibly excellent coverage. But the center spot filters are not
available for the classics and are EXPENSIVE for the new lenses.
A couple of friends and I talked about making our own. The problems
are serious (which is partly why they are expensive), but workable.
Anyone got ideas how to do it? Here are some random thoughts...
1. Color neutral materials are a challenge. Litho film is pretty
good, as is copier toner suspended in gel.
2. You can compute the function on a computer and plot it, but it
needs to be calibrated for each lens.
3. The center spots for modern lenses are not the pure cosine to the
forth function, because the lens geometry is so complicated.
4. One approach would be to photograph a white field through the lens,
and then mount the resulting negative as a filter to produce a
uniformly bright image (the lens would be the definition of its own
filter).
5. Another approach would be to calculate the filter and then print it
out using photoshop onto transparency material.
Any contributors or aiders and abbetters out there?
Date: Sat, 13 Jan 2001
From: Michael Briggs MichaelBriggs@EarthLink.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: How Could You Build A Practical Center Spot Filter?
drdagor@my-deja.com wrote:
cut...
> But the center spot filters are not
> available for the classics and are EXPENSIVE for the new lenses.
I don't think that you need have a center filter designed by the lens
manufacturer for excellent results. Heliopan markets a line of
"generic" center filters at somewhat lower cost than those of the lens
manufacturers. A Heliopan (or Rodenstock or Schneider) filter of the
right diameter would probably do a good job on a classic lens. AFAIK,
neither Fuji nor Nikon produce center filters for their lenses, so users
who want a center filter will have to buy one made by a different
company.
> A couple of friends and I talked about making our own. The problems
> are serious (which is partly why they are expensive), but workable.
> Anyone got ideas how to do it? Here are some random thoughts... cut...
> 5. Another approach would be to calculate the filter and then print it
> out using photoshop onto transparency material.
I think your last idea is the best, because it is cheap and plenty good
enough. I don't think you need to do any calculations. Just set up
some radial gradients and print out to transparency material, then take
test photographs and select the one you like. If your ad hoc center
filter gives good results, then its good for the job. For testing, I
suggest focusing the lens on a distant object, then pointing the camera
at a nearby evenly illuminated, single-toned object, perhaps a piece of
postboard in sunlight. Your testing will reveal evenness of
illumination and how much exposure compensation is needed.
I am not sure that the manufacturer's base their center filters on
mathematical calculations. They do NOT aim to produce completely even
illumination of the negative. If they did, the required exposure
compensation would be too high for convenient use. Perfectly even
illumination of the film isn't required: few scenes are evenly luminous
and the printing process can compensate for some unevenness.
--Michael
Date: Sun, 14 Jan 2001
From: Tadeuz Jalocha tjalocha@netexpress.cl
Newsgroups: rec.photo.equipment.large-format
Subject: Re: How Could You Build A Practical Center Spot Filter?
You could use sheets of Colour-diapositive material.
Expose thru the lens with cyan light and you get a yellow Center filter
if you develop in C-41.
For B/W much better than a grey one.
The first center-filter i know of was made by rodenstock and was yellow
too.
...
Date: Tue, 16 Jan 2001
From: sanking@hubcap.clemson.edu (Sandy King)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: How Could You Build A Practical Center Spot Filter?
drdagor@my-deja.com wrote:
> I've got a couple of older WA lenses with excellent coverage...
> I'm also trying to pick up one or two of the modern WA lenses with
> incredibly excellent coverage. But the center spot filters are not
> available for the classics and are EXPENSIVE for the new lenses.
I have followed this thread (including the links) and found some
interesting ideas that might be worth a try for my needs. I would certaily
be interested in being kept informed of any follow-up information that may
become available. My situation is that I have a very large lens, a 210/f/8
Super Angulon which I use with my 7X17 and 12X20 cameras. At this coverage
fall-off in illumination is quite severe. Since I do a lot of work with
this lens I would be happy to buy a center filter for a moderate price.
Unfortunatley, the only thing available for this lens (which has a 136mm
screw-in thread) is a sporadically available center filter that would set
me back $2850.00 list). Yes, that is right, no transposition of zeroes as
I first thought when quoted the price.
Thanks to those who are interested in the topic to keep me informed of any
off-list developments about buiilding one of these center field beasts.
Sandy King
Date: Tue, 16 Jan 2001
From: "Nicholas O. Lindan" nolindan@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: How Could You Build A Practical Center Spot Filter?
drdagor@my-deja.com wrote:
> I've got a couple of older WA lenses with excellent coverage...
> I'm also trying to pick up one or two of the modern WA lenses with
> incredibly excellent coverage. But the center spot filters are not
> available for the classics and are EXPENSIVE for the new lenses.
You could make a mechanical center filter that spins.
There is an old extreme WA lens that did this trick (heliogon?). The
center filter was a fan that sat in front of the lens and was powered by
the photographer's breath.
A clear filter with the right ratio of dark to light painted on it,
mounted in a polarizing filter holder and spun by a small DC motor might
do the trick.
--
Nicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com
From Leica Topica Mailing List:
Date: Sat, 20 Jan 2001
From: "Henning J. Wulff" henningw@archiphoto.com
Subject: RE: [Leica] my first test with the 12/5.6
Dan Cardish wrote:
>I've thought of that, and in fact I think Voigtlander sells a bubble level
>thingy to attach to the hot shoe. Problem is, to make sense of this I
>think you would have to use a tripod, and I generally don't use one.
>
>dan .c
>
>At 04:38 PM 20-01-01 -0800, Frank Filippone wrote:
>>You might want to consider a bubble level? It would help with the
>>horizon.... I use a Craftsman bubble level just laid on top of my
>>hood.....this does require a tripod and a flat spot on the hood! Cost is
>>about $4.
>>
>>Frank Filippone
>>red735i@earthlink.net
Dan, I have the bubble level and double shoe and they work well,
although only in horizontals. I use this handheld. If I use a tripod
I use a better level; an electronic one I carry with me on all
architectural shoots.
Another solution is one of the little shoe mounted levels and the
Voigtl,nder double shoe. You can't see the bubbles as well from the
shooting position with your eye to the finder, but they work in both
horizontal and vertical orientations.
Usually I find the light falloff unobjectionable, but if I want to
even it out Voigtl,nder makes a filter adapter that takes 77mm
filters, and Heliopan makes a relatively reasonable center filter. If
you have other center filters, any of the larger ones from 82mm on up
can be adapted and won't vignette.
Watch out for some center filters that have a sharp transition from
the grey to the completely clear; this doesn't matter for the 72mm
and longer focal lengths they were designed for, but the dof of the
12mm is such that this transition can be visible. I have an older
filter for the 90/5.6SA that's fine, but a newer one for the
72/5.6SA-XL is not. It's the same problem that the 15 Hologon filter
had and caused a visible line in even toned (sky) areas.
--
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
From: "Larry Whatley" linda_aw@ix.netcom
Newsgroups: rec.photo.equipment.large-format
Date: Wed, 17 Jan 2001
Subject: Re: How Could You Build A Practical Center Spot Filter?
If you're willing to give up some exposure range on the negative
(FP4?) you
could just expose for the edges and use a negative center filter in
printing, the advantage being that the filter wouldn't have to be a
particularly good one. But I guess that's just another way of dodging...
that being what you're trying to avoid.
- Larry Whatley
Sandy King sanking@hubcap.clemson.edu wrote
> > I've got a couple of older WA lenses with excellent coverage...
> > I'm also trying to pick up one or two of the modern WA lenses with
> > incredibly excellent coverage. But the center spot filters are not
> > available for the classics and are EXPENSIVE for the new lenses.
> >
>
> I have followed this thread (including the links) and found some
> interesting ideas that might be worth a try for my needs. I would certainly
> be interested in being kept informed of any follow-up information that may
> become available. My situation is that I have a very large lens, a 210/f/8
> Super Angulon which I use with my 7X17 and 12X20 cameras. At this coverage
> fall-off in illumination is quite severe. Since I do a lot of work with
> this lens I would be happy to buy a center filter for a moderate price.
> Unfortunatley, the only thing available for this lens (which has a 136mm
> screw-in thread) is a sporadically available center filter that would set
> me back $2850.00 list). Yes, that is right, no transposition of zeroes as I
> first thought when quoted the price.
>
> Thanks to those who are interested in the topic to keep me informed of any
> off-list developments about buiilding one of these center field beasts.
>
> Sandy King
rec.photo.equipment.medium-format
From: heavysteam@aol.comzapcrap (Heavysteam)
Date: Sat Apr 14 2001
[1] Re: Hasselblad Xpan vs 645
I haven't tried it yet, but I'm told that you won't experience fall-off
if you stop it down to f16 or f22. Has anyone tested this?
I still had fall off at f16. Don't forget that this end of the aperture
reduces sharpness because of diffraction and the lens seems to hit maxium
sharpness right around f8. The only solution I could come up with is to
bite the bullet and get the center filter. Now I have no problem using
the 45mm lens in it's maximum sharpess range. One big bonus that has
already paid for the center filter architectural exteriors. It's ideally
suited to long low buildings, and I find that I can get a very acceptible
shot with just the Xpan and a tripod instead of hauling out the 4X5.
This saves a lot of time and allows me to bring the image into the
computer with a scanner at the office instead of drum scanning a 4X5.
From rangefinder mailing list:
Date: Wed, 29 Aug 2001
From: Polak187@aol.com
Subject: xpan true PANORAMA center filter q.
Ok,
after shooting with my xpan true panorama camera :) for a while I find that
it's all I ever wanted. Their 45mm lens takes care of 95% of my needs and 30mm
that I bought just sits in the box because camera becomes little too big with
an extra finder mounted on top. But I took it for couple of climbing trips and
some deep sea fishing and camera did great. But...
I know that center filters exist for a reason. Since one came included with a
30mm I was thinking about picking one up for my 45mm. At the same time I'm
under assumption that you only need to use center filters when you shoot wide
open. If you shoot around f/8 fall off/darkening on the corners/vi^$@#! (damn
kinky word) is not as great (again my assumption). Also according to manual
there is a 1.5 EV lost in light when one uses center filters. Wouldn't
that create a real problems when shooting landscapes at dusk or dawn. Wouldn't that
destroy all shadows? I hate loosing light becasue of filters, hass/fuji lenses
are slow enough already. I also hate the fact that I have to put a $250 piece
of glass on and off the lens which makes me feel uncomfortable. Is there any
general rule for using center filters? Should I just leave it on all the time?
Matt
ps.
Word of advice: don't fish and shoot at the same time. Your camera will smell
like fish market and all the cats in the area will become your best friends
regardless if you own a dog or not :).
Matt
Date: Sat, 16 Feb 2002
From: Michel Dusariez dusariez@pano360.org
To: panorama-l@sci.monash.edu.au
Subject: Re: Center filter for XPAN
Hi,
I have always consider that grey center filters are required to
compensate a lack off coverage (quality) of some optics or from basic
bad construction.
If an optic is well constructed the front and rear lenses will be big
enough to give same lighting on all surface of the film as well as
the edges.
If not, the optic is not constructed to such film size. I am surprise
that such well-known brands propose such optic with lack of coverage.
In addition the center grey filter will reduce the usable opening
diaphragm.
As everybody knows an optic must fully cover a circle of size of the
diagonal of your film size.
Michel DUSARIEZ
Optician
>Marty, Center filters are used with any lens that covers a wide viewing
>angle to compensate for the falloff of light from the center to the corners
>of the image, which is not a defect in the lens design but a limitation of
>physics. A center filter is dark gray at the center & changing gradually in
>a radial direction to clear at the edge. The wider the angle of view of the
>lens, the darker the center is. A center filter is typically matched by the
>manufacturer to a particular lens that it will be used with since in general
>light falloff varies with each lens. Thus, I would definitely get the one
>that Hasselblad makes for the Xpan 45mm lens. It has 49mm threads & the
>hood for the 45mm Xpan lens will mount on the 45mm with the center filter in
>place. It's Hasselblad part #54453 & you can read a description of it at
>this URL:
>
>http://www.hasselblad.com/products/cameras/xpan45.html
>
>The only drawback is that is has a list price of $234. However, bargaining
>with a dealer who wants to make a sale should help a bit. I'm not positive
>what the etiquette on this list is regarding recommending particular dealers
>but if you contact me offline I can suggest a good one with reasonable
>prices.
>
>Regards, Ted
"MMagid3005@aol.com" wrote:
>
>> Dirk, Kerry & Ted --
>>
>> Thanks for your comments, they are very helpful. I'm not familiar with
>> center filters. Is there a particular brand/model that you use or
>>recommend?
>>
>> Marty
--
http://www.pano360.org/
Michel DUSARIEZ
UNLIMITED FIELDS RESEARCH PANOPTIC IMAGING asbl
Date: Sat, 16 Feb 2002
From: ralph fuerbringer rof@mac.com
To: panorama-l@sci.monash.edu.au
Subject: Re: Center filter for XPAN
The foremost optical designer of the 20th century was L. Bertele, at 19 the
designer of the ernemman f1.8, subsequently all the sonnars plus the biogon
the benchmark wide angle. In a famous article in grossbilde technique in the
fifties he made the statement that fall off from the center to the edge in a
an extreme wide angle lens was inevitable. Light falls off on the square and
the distance from the center of the rear element is way shorter than the
distance to the corner. He stated that he had managed to reduce modestly
the effect in his design of the biogons,21 to 75mm. The 35mm apo-grandagon
used in my vistashift-612 cameras, is discussed, illustrated on Robert
Monaghan's benchmark medium format site
http://medfmt.8k.com/mf/vista612.html
This lens covers more than twice the area of the famous 38mm biogon on the superwide
hasselbad. It is a superlatively designed lens with amazing lack of
distortion, but without a center filter the light fall is over
10 to 1. The center is a few mm from the film, the corners on 612 hell and
gone. If you do your own printing, expose for weak light at the edge
you might away without a center filter. The 45 apo-grandagon has worked for
me ok w/o a center filter. If you shoot transparencies you should use a
center filter on both, and incidently none of the regular center filters
offered by any one fully compensates for the actual falloff. As Bertelli
explained you can compensate in the lens design to minimize the effect but
you can't overcome it completely. Now we are at over twice [the] coverage he was
concerned with. Center filters are a wonderful tool. Way back goerz put a fly
swatter in the center of an extreme wide angle. Vibrating it was supposed
to even out the light. Lots of luck. Hooray for center filters. ralph
From Panoramic Mailing List:
Date: Thu, 14 Feb 2002
From: Kerry Swartz kerry@swartz.net
Subject: Re: XPAN
MMagid3005@aol.com said:
> I'm thinking about buying a Hasselblad XPan, and I remember past discussions
> on this list about it so I was wondering if there is an archive I could find.
> I also heard that the XPan is made by Fuji and that Fuji makes an identical
> camera but they are prohibited from the U.S. market. I would appreciate any
> comments on the XPan, especially by those who have owned them, and on how to
> get one of the Fujis. I live across the Detroit River from Ontario -- would
> that help?
>
> Marty
I've had an XPan since they were first released and quite happy with it.
I've used it regularly and it is still in nice shape. My friend bought one
at the same time, has used it less and the finish is awful; I've heard from
others about paint easily chipping off. The 45 and 90 lenses are very good.
I've not opted for the 30mm since it's far too expensive relative to the
price of the XPan body and sell and Xpan which I believe is called the TS1
or something like that. It's silver and usually available in Asian markets.
I've seen the odd one on ebay.
Hasselblad's XPan seems to have the best level of construction when you
compare it to strictly Fuji cameras - more metal instead of plastic, tighter
joins, smoother transport.
The most required accessory would be the graduated center filter for the
45mm lens which allows you to use slide film without much or any falloff,
but you essentially lose a stop or more making it a very slow lens.
I hope these comments find some listening ears since my three repeated posts
about my Olympus E10 appear to have largely gone either unnoticed or ignored
by other members of this list.
Kerry
--
Kerry Swartz [photographer]
online portfolio: http://www.ksphotos.com
From panoramic mailing list:
Date: Thu, 14 Feb 2002
From: Ted Baker ted@ldeo.columbia.edu
Subject: Re: XPAN
Marty, I've had an Xpan with 45mm & 90mm lenses for about a year & a half
now & have been totally happy with it. Design, construction & finish are
excellent. Kerry Swartz is right -- get the center filter for the 45mm lens
for sure (not needed on the 90mm). You'll lose a stop but you'll get even
illumination from corner to corner in panoramic mode. I leave it on the
45mm & have found that I don't need a skylight or UV filter. I use the XPan
mostly in panoramic mode but being able to switch (even in mid-roll) to
normal mode is a big plus. If you find someone who imports (on their own)
the TX-1 n the gray market, be advised that you will not be able to get a
Fuji U.S. warranty with it. Perhaps the importer will offer their own
warranty but I would inquire very closely as to how many TX-1's they have
actually repaired & how many parts they stock. This is in no way a
criticism of the TX-1, just a heads-up in case it ever needed service. Feel
free to contact me offline -- I'll be happy to discuss any of the above &
more if you want.
Regards, Ted
Regards, Ted
"MMagid3005@aol.com" MMagid3005@aol.com wrote:
> I'm thinking about buying a Hasselblad XPan, and I remember past discussions
> on this list about it so I was wondering if there is an archive I could find.
> I also heard that the XPan is made by Fuji and that Fuji makes an identical
> camera but they are prohibited from the U.S. market. I would appreciate any
> comments on the XPan, especially by those who have owned them, and on how to
> get one of the Fujis. I live across the Detroit River from Ontario -- would
> that help?
From Panoramic Mailing List:
Date: Thu, 14 Feb 2002
From: Ted Baker ted@ldeo.columbia.edu
Subject: Re: Center filter for XPAN
Marty, Center filters are used with any lens that covers a wide viewing
angle to compensate for the falloff of light from the center to the corners
of the image, which is not a defect in the lens design but a limitation of
physics. A center filter is dark gray at the center & changing gradually in
a radial direction to clear at the edge. The wider the angle of view of the
lens, the darker the center is. A center filter is typically matched by the
manufacturer to a particular lens that it will be used with since in general
light falloff varies with each lens. Thus, I would definitely get the one
that Hasselblad makes for the Xpan 45mm lens. It has 49mm threads & the
hood for the 45mm Xpan lens will mount on the 45mm with the center filter in
place. It's Hasselblad part #54453 & you can read a description of it at
this URL:
http://www.hasselblad.com/products/cameras/xpan45.html
The only drawback is that is has a list price of $234. However, bargaining
with a dealer who wants to make a sale should help a bit. I'm not positive
what the etiquette on this list is regarding recommending particular dealers
but if you contact me offline I can suggest a good one with reasonable
prices.
Regards, Ted
From Panoramic Mailing List:
Date: Thu, 14 Feb 2002
From: Peter Marshall petermarshall@cix.compulink.co.uk
Subject: Re: XPAN
...
Marty,
I think it is worth getting an XPan if you get the 30mm lens. The 45mm is
fun to work with, but the 30mm almost gets you into real panoramic
territory. It isn't cheap, though I bought mine secondhand which helped.
A centre filter is essential with the 30mm. With the 45mm you can shoot
without it on colour neg and black and white, but I think you really need
it for transparency, though if you stop down well you might get away with
it.
If I wasn't going to buy the 30mm I think I would be better off with a 120
format camera and a wide angle, cropping down to panoramic format when I
wanted to. Something like a Mamiya 7 with 43mm or 50mm would give similar
results, but also enable me to do other things. And of course there is a
wider range of lenses.
he finish is not too great - I've used mine less than a year and it looks
pretty worn. I think the Fuji is only supported in Japan, which is a long
way to go for repairs.
Peter Marshall
Photography Guide at About http://photography.about.com/
email: photography.guide@about.com
Date: Tue, 19 Feb 2002
From: Peter Marshall petermarshall@cix.co.uk
To: rmonagha@post.cis.smu.edu
Subject: Re: photoshop center filter effect? Re: XPAN
>
> I would think you could take a B&W; photo of a uniformly lighted (white)
> wall, scan that negative, and have a custom mask for photoshop exactly
> balancing the dropoff (darker in center as brighter wall)?
It is an idea, and so long as you remembered the diffusion to get
completely rid of any texture would sort of work, though I think the
effect is aperture dependent, so it would only work roughly at other
apertures. You might alternatively just use a mask made using Photoshop's
radial fill with a little tweaking.
There are very few subjects where it is important to get absolutely even
illumination across the frame in any case. I know that it actually is
uneven in my pictures, but it is often not noticeable, seldom disturbing
and in some cases beneficial.
I think you have to remember that many of the people who contribute to
mailing lists are armchair theorists who don't get on with taking
pictures. If you take negatives and get your work handprinted (or do it
digitally) it doesn't seem a big deal to me. I have several hundred rolls
of colour neg that say its not really a problem.
Peter Marshall
petermarshall@cix.co.uk
From: "Kerry L. Thalmann" largeformat@thalmann.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: 80mm Super Symmar XL--users? Comments?
Date: Sun, 07 Apr 2002
Just a couple additional data points based on the Schneider relative
illumination curves. All of the 90mm Schneiders (90mm f8, 90mm f5.6 and
90mm f5.6 XL) have a percent relative illumination in the low 40s (about
40.5% - 44%) at the corners of a 4x5 image (assuming image diagonal of
153mm and no displacements) at f22 and infinity. By comparison, the
110mm Super Symmar XL is in the high 40s (looks like about 48% give or
take).
For me personally, I've always found a center filter necessary for
anything shorter than 90mm on 4x5. Specifically, for my personal needs
and sensitivity, I've found the 75mm f4.5 Nikkor SW, 75mm f6.8
Grandagon-N and 80mm f4.5 Super Symmar XL to all benefit substantially
from the use of a center filter. On the other hand, I've never found
the fall-off sufficient to warrant a center filter on lenses 90mm and
longer. Based on the numbers, it looks like I am personally willing to
tolerate fall-off in the corners down to about about 40%, but anything
less and I prefer the center filter.
That's just a personal data point, but it does show how you can compare
the fall-off of lenses you are contemplating against ones you already
know. For example, if I had done this excerise before testing the 80mm
SS XL, I would have already known the fall-off was most likely worse
than the 75mm I'd been using with a center filter (Nikkor SW - which
based on my experience has fall-off very similar to the 75mm f5.5 Super
Angulon and 75mm f4.5 Grandagon-N). It also tells me that I would
probably require a center filter when shooting 5x7 with the 110 SS XL
(something I've also verified experimentally).
Kerry
--
Kerry L. Thalmann - Large Format Images of Nature
http://www.thalmann.com/
Kerry's Large Format Homepage
http://www.thalmann.com/largeformat/
From panoramic mailing list:
Date: Mon, 01 Apr 2002
From: ralph fuerbringer rof@mac.com
Subject: Re: Low tech question.
Medium tech filter and ring info, many are unaware of: in respect to wide
angle lenses, many lose image circle when you screw anything into the front
threads, not that swinglens cameras have/need wide angle lenses at all. I am
referring to the super angulons, apo-grandagons, super symmar xl aspherical.
only rodenstock mentions this problem, publishing these startling,
threatening figures: the 55mm apo-grandagon loses 9mm from the diameter of
its image circle and its angle is reduced from 110 to 107 degrees when its
dedicated center filter is screwed in. you buy a center filter to get better
edge coverage, but hey catch 22 the far edge is eliminated altogether by
the filter. Further degrading of the image is from reflection of the screw
in ring on the film,this also in the rodenstock center filter brochure.
solution: for my vistashif-612 tweak of the brooks veriwide
(http://medfmt.8k.com/mf/vista612.html) i use over the lens filter
mounts, into which i remount the center filters. all center filters are
actually in step up rings to begin with. For example the dedicated center
filter for the 55 apo-grandagon has the 67mm lens threads on the small end
and 86mm on the front. also in many the retaining rings are way to wide and
again can cut image. heligon center filters are the worlds worst in that
regard.
ralph
> From: AJNECP@aol.com
> Date: Mon, 01 Apr 2002
> To: panorama-l@sci.monash.edu.au
> Subject: Re: Low tech question.
>
> I said adapter rings, I meant to say step-up rings.
>
> AJ
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Newbie Questions- Soft focus and Center Filter
Date: Fri, 17 May 2002
keithmitchell@usit.net wrote:
>First what is a soft focus lens?
>Second, what is a center filter and why do they cost so much?
>
>Thanks,
>Keith Mitchell
>keithmitchell@usit.net
....(soft focus..)
Center filters are made to correct, at least partially, the fall off
of illumination from center to edge of an image. This fall off is an
inherent property of lenses which are made to reproduce a flat surface
onto another flat surface without distortion, a property called
rectilinear. Most camera lenses are designed to be rectilinear. An
exception is the fish-eye type wide angle lens. Because the image is
compressed toward the edge (it looks as though one were seeing it
reflected in a sphere) there is little fall off.
Some lenses employ a principle called a tilting entrance pupil,
which effectively makes the lens faster for light coming in at an
angle. This principle can partly correct fall off, but most of it
remains. For lenses with more than moderately wide angle coverage the
darkening of the image away from the center can become important,
espeically when using positive color film. So, a center filter is used
along with stopping down the lens. The center filter allows more light
to enter at angles from the edges and reduces the light at the center,
making it more uniform.
Center filters must, in general, be matched to the lens they are
used with in the sense of the size of its front element and coverage
angle. They do not have to be made specifically for a particular lens.
The center filter should also be matched to the fall off rate of the
type of lens its to be used with.
Center filters are expensive partly because they require some
precision in manufacture. The coating must be color neutral and effect
all colors to which film is sensitive. It is generally a vacuum
deposited metal film. In order to work properly it must taper from
center to edge in a prescribed manner and to a precribed density. Not
cheap to make. They are also generally made in small numbers so
whatever savings might be made from mass production techniques is not
available.
Keep in mind that the integrated circuits used in electronics would
cost a fortune if made in small quantity, they are very cheap because
they are made by the ton. This sort of economy is not available to
something as specialized as a center filter.
---
Richard Knoppow
Los Angeles, CA, USA.
dickburk@ix.netcom.com
Subject: Re: advice needed on centre filter for 58mm SA XL
From: Jon vze249jf@verizon.net
Newsgroups: rec.photo.equipment.large-format,w.stubbs@legend.co.uk
Date: Fri, 19 Jul 2002
Hi Wayne,
I just bought the Schneider 3B center filter for my 58mm SAXL. It is of a
very good quality.
I didn't find this to be much help:
http://www.schneideroptics.com/photography/accessories/center_filters/
But B&H;'s web site says this:
67mm Center Filter (#3b) for 80mm f/4.5 and 110mm f/5.6 Super Symmar XL
Lenses and 58mm f/5.6 XL and 90mm f/8 Super-Angulon Lenses
I don't know if the 3B will work on the Sinaron... does it really need a CF?
The 58mm SAXL definitely needs the CF on 4x5--I have found it necessary also
when shooting chromes with lots of sky on 6x12.
Jon
P.S. You may have a tough time getting a filter on the front of the CF
(86mm). Schneider told me that only the EW series will work with CF's. I had
Steve Grimes make me a slip on mount for 4x4 (100mm) gels. It was cheaper
than the one glass screw-in filter I was going to buy and it took him a week
to make it.
Here:
http://www.skgrimes.com/
> From: w.stubbs@legend.co.uk (Wayne Stubbs)
> Newsgroups: rec.photo.equipment.large-format
> Date: 18 Jul 2002
> Subject: advice needed on centre filter for 58mm SA XL
>
> I have just purchased a 58mm xl lens. In the next couple of weeks I
> will be buying the centre filter for the lens. I understand that this
> filter can also be used on the 90mm f8 super angulon as well.
>
> I also have a Sinaron 75mm f4.5 lens. Does anyone know wether the
> schneider centre filter will work well with this lens ?
>
> As anyone tried to do this and got exceptable results ?
>
> many thanks,
>
> Wayne Stubbs
From camera makers mailing list:
Date: Tue, 03 Sep 2002
From: Robert Mueller r.mueller@fz-juelich.de
Subject: Re: [Cameramakers] Re: Resolution of Metrogon
Thanks for the advice on the center filter for the Metrogon. I actually
had a different problem in mind. As I understand it a piece of flat glass
adds spherical aberration. Someone in this group reported that the
Metrogon was calculated with this in mind by including compensating
aberration of the opposite sign so optimum resolution would be reached when
one of the center filters was in place. (These things are pretty
thick.) Conversely, I have a publication (in fact, two of them) giving
data for the glasses, radii and spacings of the Metrogon and neither
mentions any filter. Then again, just because the published designs do not
include a center filter does not mean B&L; did not tweak the design for the
military optics. Thus, I simply have no idea how much difference the
filter makes and, sadly, I have never seen a clear center filter for these
lenses.
What you report on the importance of uniform exposure is very revealing and
makes clear why looking only at resolution data is a mistake and the whole
situation must be considered in the context of making real photos.
Thanks again!
Bob
you wrote:
>resolution could actually be higher with the center filter, since excess
>exposure (1 stop) can cost you 20% or more of resolution potential, per
>example tests cited at http://medfmt.8k.com/mf/lenstest.html by Roger Hicks
>in Jan 2002 Shutterbug in testing wide angle 21mm on Pan F film. If the
>center filter enabled uniform exposure without a center highlight, you
>would avoid these losses (and more likely 2 or more stops overexposed without
>the filter, so even more of a resolution hit?).
>
>The losses from a decent flat filter to MTF is on the order of 2% or so
>for a good filter, and for a cheapy no-name not so flat filter, maybe 10%
>at high end, per Erwin Puts estimate (he is a noted Leica lens testing
>guru etc. However, this assumes that any focus shifting effects of the
>filter are compensated in setup.
>
>I find this a bit disconcerting (and not often discussed, hence notable), as
>it means relatively minor exposure errors or differences between systems (and
>by implications, developing differences between runs) can have as much of an
>impact on lens test results as the differences between mfgers (e.g. Leitz R
>vs Nikon etc. ) ;-)
>
>But my bet would be that the impact and benefit from avoiding over/under
>exposure would outweigh the minor losses from the filter itself...
>
>* Robert Monaghan
From camera makers mailing list:
Date: Wed, 04 Sep 2002
From: Michael Briggs MichaelBriggs@earthlink.net
To: cameramakers@rosebud.opusis.com
Subject: [Cameramakers] Re: Cameramakers digest, Vol 1 #474 - 7 msgs
cameramakers-request@rosebud.opusis.com wrote:
> Thanks for the advice on the center filter for the Metrogon. I actually
> had a different problem in mind. As I understand it a piece of flat glass
> adds spherical aberration. Someone in this group reported that the
> Metrogon was calculated with this in mind by including compensating
> aberration of the opposite sign so optimum resolution would be reached when
> one of the center filters was in place.
I assume that the center filter is used in front of the Metrogon? If so, then,
for the photography of distant objects, the mere fact of having a flat uniform
thickness filter in front of the lens does NOT introduce spherical abberation.
For distant objects, the arriving light rays are very close to parallel -- the
effect of a flat uniform thickness piece of glass on parallel light rays is to
slightly shift the rays in a parallel manner -- with an object at infinity this
isn't noticeable.
Conversely, if a flat uniform thickness piece of glass is inserted into a beam
of convergent rays, spherical abberation will be created. This would be the
case for a filter behind a lens, or a filter in front of a lens when the lens
is focused on a close object. If you are doing closeups or using a filter
behind a lens, you should focus with the filter in place -- it changes the
apparent distance.
Compared to other filters, a center filter has some complicated effect on
abberations. If you a lens without a center filter, the light rays that reach
the film have arrived with equal probability over the front of the lens (at
least the part of the glass used at the taking aperture). If you use a center
filter, then the light rays at the edge have a higher probability of reaching
the film. If the abberations contributed by the outer radii are different from
the inner, then the mean abberation will be changed. I don't think there is
any simple way to predict this effect. For a really wide-angle lens, the
improvement in exposure uniformity due to using a center filter is likely to be
more important.
--Michael
From: Bob Salomon bob@hpmarketingcorp.com
Newsgroups: rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: Re: Where to buy Schneider or Rodenstock filters?
Date: Tue, 08 Oct 2002
Xosni@gega.net (Xosni) wrote:
> I'm fed up with those Hoya filters. I want to try quality filters now-
> I'm talking specifically about #29 (dark red) filter for B&W.; Where
> can I get Schneider or Rodenstock filters in the US (VA)? And which
> offer the best quality?
>
> regards,
> Xosni
Rodenstock only makes Graduated Center Filters. All other Rodenstock
filters are Heliopan.
--
HP Marketing Corp. www.hpmarketingcorp.com Ansmann, Braun, Combina,
DF, Ergorest, Gepe, Gepe-Pro, Giottos, Heliopan, Kaiser, Kopho, Linhof,
Novoflex, Rimowa, Rodenstock, Sirostar, Tetenal ink Jet and cloths,
VR Frames, Vue-All archival products, Wista, ZTS
Date: Thu, 24 Oct 2002
From: Jim Brick jbrick@elesys.net
To: hasselblad@kelvin.net, hasselblad@kelvin.net
Subject: Re: [HUG] Scanning Xpan 35mm Negatives
Manu Schnetzler wrote:
>Actually, Epson TWAIN doesn't have any problem with arbitrary size. I've
>scanned xpan negs with it with good results (such as
>http://www.schnetzler.com/PAW/week_39.html).
>
>The only problem I see is a bit of vignetting but that's a due to a lack
>of center filter on the camera, not to the scanner.
>
>Manu
Over the years, some of my best (and most sold) photographs are those taken
with a very wide angle lens and no center filter. The edge darkening quite
often (most often for me) enhances the photograph, especially when printed
20x24 or 30x40. You don't really notice the drop off around the edges but
it really helps to keep your eyes focused within the image rather than
having them run off the edge of the print.
You Xpan photograph (very nice photograph) falls into this category in my
view. The drop off is good.
:-)
Jim
From: "John Cremati" johnjohnc@core.com
To: cameramakers@rosebud.opusis.com
Subject: Re: [Cameramakers] center filter
Date: Tue, 7 Jan 2003
Rather than using a silver based emulsion as the final emulsion or
film , you could use a glass coated with gelatin with a aniline dye (
aniline dyes are generally transparent) , sensitize the emulsion with
ammonium dichromate .. Aniline dyes I believe is what Kodak uses in many of
their gelatin filters.. The first image would be silver based fine grained
negative film but then you would contact print the gelatin dye coating to
create the filter.. In essence what you are doing is making a carbon print
of the light fall off.....
The big problem would be to determine which dye has the neutral density
characteristics...Creating a center filter in red, yellow , orange or green
filter would probably very easy information to come by as isochromatic
photography is based on the various dyes ability to absorb different parts
of the spectrum of light.., but I would not even know where to begin on
creating a neutral density dye...
Another problem would be to make the filter so the fall off is equal to that
of the lens when placed in front of it....
jc
Date: Wed, 05 Mar 2003
From: Robert Feinman robertdfeinman@netscape.net
Newsgroups: rec.photo.equipment.large-format
Subject: Fixing wide angle vignetting using Photoshop - New Tip
I've added two new tips on adjusting darker corners when using ultra
wide angle lenses or wide aspect ratio formats to my web site. Using
Photoshop can help avoid needing a center filter.
I've also updated some of my Hawaii photos taken with my 4x5. The
views of the interior of the Haleakala volcano crater came out quite well.
Finally, a little off topic. If you need a change from lugging all the
large format equipment around you might be interested in my ebay
auction of a Tessina 35mm subminiature camera. Smaller than a pack of
cigarettes.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item;=2915505279
--
Robert D Feinman
robertdfeinman@netscape.net
Landscapes, Cityscapes, Panoramas and Photoshop Tips
robertdfeinman.com
Date: Thu, 10 Apr 2003
Newsgroups: rec.photo.equipment.medium-format
From: Gavin Shaw gavin.shaw@zetnet.co.uk
Subject: Re: Graduated ND Filter for G617 via photoshop layer?
from panstitcher@yahoo.com (Larry) contains these words:
> Hi,
> I would like to construct an accurate photoshop layer
> that can be used as a post-processing fix up in place of
> a real graduated neutral density filter. For Fuji G617 with
> 105mm F8.
> Yes, I recognize it is not the same as a real filter and
> the exposure can't be as accurate.
> I use color print film.
> I would try to hit perfect exposure for a point halfway between the center
> and the ends. Then slightly darken
> the center and slightly brighten the two ends. With even gradation
> in between.
> Would the values be a function of the F stop? Or is the drop off consistent
> despite aperture changes.
> Any tips appreciated.
> thank you
> Larry
Larry,
There's a tutorial using a multiplication layer for your very lens on
Luminous Landscape:
http://www.luminous-landscape.com/tutorials/panorami.shtml
I expect the graduation could change slightly with F-stop. Maybe you
could create an empirical multiplication layer for a range of F-stops
by photographing an evenly lit plain surface, scanning it, softening it,
inverting it. Tricky to find something big enough to photograph without
close focus capability, but I guess you wouldn't need an in focus
surface!?
--
Gavin
http://www.users.zetnet.co.uk/gshaw/
[Ed. note: thanks to Robert Mueller for sharing these ideas and tips...!]
From: Robert Mueller [r.mueller@fz-juelich.de]
Sent: Fri 5/30/2003
To: Monaghan, Robert
Subject: Center Filters not at the center!
I have long been longing for a clear center filter for my Metrogons and
just read through your collection of postings on the
subject. Unfortunately, I don't know the correct way to add to the
material so I am just making a suggestion for a different, though limited
approach.
Making a proper, graded center filter is not easy and designing it
(figuring out what the optical density versus radius must be) is also not
trivial as far as I can see. In the above comments I saw some worries
about the "flower pedal" style of filter but some of the concerns seem
excessive. For example, if you "glue" a foil to the glass of a large,
clear filter, I see no need to worry that the foil be precisely flat if it
is truly opaque. It would help to have the foil black but with aluminium
that is easy to achieve; black anodize, practically a household operation,
though you need a suitable power supply. If you are careful you can
remove the foil and try again until you reach adequate uniformity. I do
not completely share the concerns about loss of resolution; such an effect
will result from extra diffraction but the B&L; filters were good enough for
the military aerial photos and the military is not well known for making
compromises. A few extra thousand dollars for a graded density filter
would upset nobody if the results were substantially better. According to
one book I have, astrophotographers find the Metrogons not so good unless
stopped down somewhat (but that information is ancient and may apply to the
4 -element variety only; I don't know!) For this small aperture
diffraction from the "pedals" might just disappear into the background of
the diffraction from the lens itself.
For those who want a nicer end product, after determining the correct pedal
shape, you can deposit silver onto the well cleaned glass (the way mirrors
were once made) and etch away what is not required to leave the correct
pattern. The bad news is that this is not black on the lens side, but I
suspect the B&L; filters are also mirror-like, though the metal is probably
chromium or Inconel, which adhere better (chrome is wonderful and I have
been able to wash glass with this coating without loss of the chrome or
other damage.) I believe Inconel is especially useful if you attempt the
graded filter type of center-filter because the color is quite neutral;
however, I have great doubts there will be many graded, evaporated filters
made by readers of this group. The equipment and skills are probably quite
rare.
If anybody has one of the asterisk-type ("Flower pedal") filters it would
be wonderful if a photo could be posted showing as precisely as possible
how this should be shaped. A size reference would be highly desirable.
Better would be a precise drawing but that needs more work so probably
nobody wants to make it.
For the occasional camera offering no swings, tilts or other movements and
only used at a fixed object distance (infinity is fixed enough!), why not
put a filter at the film plane! There the demands on optical quality are
easier to meet and the density is easy to determine. Photograph a wall and
measure the density versus position (really only density versus radius
ought to be needed unless something is wrong, a simple, one-dimensional
problem.) I would even try just producing this density function from a
photo of the wall and with appropriate processing to get the correct gamma
and center density. Then use this just in front of the film, not up front
at the lens. I admit the loss of flexibility going with movements is not a
trivial matter but some camera already sacrifice the flexibility and there
the method might be a quick and dirty way to accurately flatten the
exposure over the film area. Something similar to this was suggested
above but to be placed at the lens. Here the demands on optical quality
are much more stringent, the main motivation for moving the filter to the
film plane. It is probably better to use color film for this job because
the pattern will be in transparent dyes, but there is a major problem, the
masking tint in the film base of negative materials. (Positive materials
have a clear base but put the most light in the middle, exactly what is
unwanted.) Dyes will scatter light less than the tiny grains of silver in
black and white films, though with the filter near the film to be exposed
this should not be too bad. I believe there are some rare film types
making negatives in color without the masking color.
The above mentioned constraint on distance is weak; close-ups would be a
problem but I expect no serious trouble at reasonable distances. Using a
very wide angle lens for close-ups is probably not too common; though I can
imagine applications where it is the best (only?) solution.
Bob
falloff pattern,
>which can be imaged negatively to yield ideal center filter pattern, yes?
>;-) the trick is to get the right magnification, which is to say, to
>reverse the light thru the negative, back thru the lens, with a "filter"
>of the right size in place. The filter could be a sensitized UV filter,
>sensitized by liquid emulsion, yes? Then develop it, to get a "negative"
>of the negative, that is, the positive center filter image you need.
>This assumes you can shine light thru the negative of the uniformly
>lighted wall, back thru lens, to sensitized filter in front of lens. It
>doesn't have to image at infinity, it should be the right size and density
>for near infinity (or wall distance etc.)?
>
>If you can find a film base that is clear enough, and many films are
>pretty decent, including slides ;-) you can simply
>try the above with the film and use the developed film in an empty filter
>ring, yes?
>
>just some late night thoughts - gotta run, closing up the bldg here ;-) bobm
--->
From: "Nicholas O. Lindan" nolindan@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: More cheap 8X10 center filter ideas?
Date: Fri, 18 Jul 2003
"J Stafford" john@stafford.net wrote
> Forgive me for being little off-topic, but making up for light fall-off
> during the printing rather than using a graduated filter in the making of
> the image is wildly different in terms of outcomes. In the printing method
> one part of the negative is either over exposed or underexposed, so the
> curve (gamma?) is off.
Yup.
To have a chance of working this technique would require using a straight-
line film (constant gamma: no shoulder) with great latitude. Tmax-100?
I would recommend trying it - shouldn't take more than an hour or two
of darkroom time and 2 sheets of film.
Looking at:
http://www.kodak.com/global/en/professional/support/techPubs/f32/f002_0545ac.gif
and doing a bit of work with ruler and pencil, I come up with the following steps
making the center filter:
Develop for 9 minutes - this produces a 1:1 slope so that doubling the exposure
doubles the density
Expose in the camera so the corner of the negative has a density of 0.8 OD -
this point is the beginning of the film's linear response.
Expose the positive filter so the center is at 0.8 OD.
That should do it.
Success is achieved when a sandwich of the negative and positive
filter films yields a uniform grey, yah?
When taking pictures one again has to use T-Max 100 developed for 9 minutes
in T-Max RS at 75F.
The developer doesn't have to be T-Max RS (though it is the one Kodak recommends
for the most linear response).
Yeesh - time to stop talking about it and just do it. Paralysis by
analysis is what we have here.
--
Nicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com
From: artkramr@aol.com (ArtKramr)
Newsgroups: rec.photo.equipment.large-format
Date: 18 Jul 2003
Subject: Re: More cheap 8X10 center filter ideas?
>Subject: Re: More cheap 8X10 center filter ideas?
>From: john@stafford.net (J Stafford)
>Date: 7/18/03
>
>Stacey fotocord@yahoo.com wrote:
>
>> I've got an old brass wide angle lens for my 8X10 that is interesting but
>> has a bunch of light fall off. I'm thinking there must be a way of
>> making/using a "center filter" in the enlarger I use as a light source for
>> contact printing,[...]
>
>Forgive me for being little off-topic, but making up for light fall-off
>during the printing rather than using a graduated filter in the making of
>the image is wildly different in terms of outcomes. In the printing method
>one part of the negative is either over exposed or underexposed, so the
>curve (gamma?) is off.
Corner fall off means information is lost in that area. Trying to correct it on
the printing does not bring back that information. It MUST be corrected in the
shooting or it will not solve the corner fall-off problem as far as information
in the corners is concerned..
Arthur Kramer
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer
From: artkramr@aol.com (ArtKramr)
Newsgroups: rec.photo.equipment.large-format
Date: 16 Jul 2003
Subject: Re: making a center filter
>Subject: making a center filter
>From: Robert Feinman robertdfeinman@netscape.net
>Date: 7/16/03
>
>I've always thought it might be possible to make a
>center filter yourself, rather than pay the $$$ that
>they cost.
>The idea would be to photograph a uniform surface
>which would produce a negative with a darker center.
>This would then be cut to size and mounted in front
>of the lens. Being close to the the lens it would be
>out of focus and thus the grain wouldn't affect the
>image.
>The difficulty comes with trying to get the scale
>of the negative right as well as the density and
>contrast.
>Any thoughts?
>
>I've devised a proceedure using photoshop to correct
>vignetting, but it relies on film latitude to capture
>the brightness range and thus isn't good for transparencies.
>You can read about it in my tips, if you're interested.
>--
>Robert D Feinman
>robertdfeinman@netscape.net
>Landscapes, Cityscapes, Panoramas and Photoshop Tips
>http://robertdfeinman.com
Simple. Do this. set up your camera in front of a white or gray sheet. Using
the lens you want to correct make an exposure where the center of the image ia
a middle gray. Develop the film. The image on the film now represents the
falloff of the lens. Now make a reduced image to fit the lens. You now have a
reasonably good center filter.
Arthur Kramer
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer
From: John Stafford john@stafford.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: making a center filter
Date: Wed, 16 Jul 2003
Robert Feinman wrote:
> I've always thought it might be possible to make a
> center filter yourself,[...]
> The difficulty comes with trying to get the scale
> of the negative right as well as the density and
> contrast.
> Any thoughts?
A center filter need not be graduated. You can have, for example, an
evenly filled, transparent, symmetrical star-like shape imprinted upon
or placed upon a clear filter. I can post a scan of just such a filter
this evening if you like.
Date: Wed, 16 Jul 2003
From: Robert Feinman robertdfeinman@netscape.net
Newsgroups: rec.photo.equipment.large-format
Subject: making a center filter
I've always thought it might be possible to make a
center filter yourself, rather than pay the $$$ that
they cost.
The idea would be to photograph a uniform surface
which would produce a negative with a darker center.
This would then be cut to size and mounted in front
of the lens. Being close to the the lens it would be
out of focus and thus the grain wouldn't affect the
image.
The difficulty comes with trying to get the scale
of the negative right as well as the density and
contrast.
Any thoughts?
I've devised a proceedure using photoshop to correct
vignetting, but it relies on film latitude to capture
the brightness range and thus isn't good for transparencies.
You can read about it in my tips, if you're interested.
--
Robert D Feinman
robertdfeinman@netscape.net
Landscapes, Cityscapes, Panoramas and Photoshop Tips
http://robertdfeinman.com
From: stacey fotocord@yahoo.com
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Mamiay 7 43mm- was Camera suggestions?
Date: Wed, 29 Oct 2003
Bill Hilton wrote:
>>>Bill Hilton wrote:
>>>
>>> Mamiya can do this with this lens because
>>> there's no mirror in a rangefinder and the effect apparently is to
>>> greatly reduce distortion and light fall off
>
>>From: stacey fotocord@yahoo.com
>
>>It may reduce distortion but it DOESN'T reduce light fall off, if anything
>>it will have more.
>
> "More" than what? I don't see any problems with mine, even shooting a
> place like White Sands, where fall-off should be readily evident.
Well another poster who uses this lens said he needs a center filter to get
rid of =all= of it. It may not be visible in many of your uses and neither
is it visible with SLR wide angles in many uses, but it is there.
>
> Do you actually have this lens or is this just a theory of yours? If you
> have it can you post an example showing the problem?
>
Chill out dude.. ANY super wide lens is going to have some light fall off,
it's against the laws of physics for it not to, no matter how much you paid
for it! A non-retrofocus lens doesn't avoid the cos^4 law in fact is likely
to suffer more from it than a retro focus lens would be, but the retro
focus will have more distortion.
Here's a post I found doing a google search, I'd assume a 90mm on 4X5 isn't
even as wide as the lens you're talking about?
-------------------------
Dean Shough , jul 01, 1999; .
The standard formula for off axis light fall off is (cos(theta))4. A 4 by 5
inch piece of film has a diagonal of 6.4 inches = 163 mm. The angular half
field of view for a 90 mm lens is arc tan( 0.5 * 163 mm / 90 mm ) = 42
degrees. Cos(42 degrees) = 0.74. Raise this to the fourth power and the
corners receive 30% of the light the center receives - almost two stops
less than the center! If the lens is tilted or shifted, the fall off will
be worse.
Some notes on the cos 4 light fall off:
This is for an ideal lens with no vignetting.
Closing down the lens will help only if the lens is vignetting.
One cos factor comes from the obliquity of the circular aperture - the
aperture appears to be an ellipse to the off axis ray.
Another factor of cos comes from the light striking the film at an angle.
Two final factors of cos come from the increased distance between the
aperture and the off axis portion of the film being illuminated.
Some lenses differ markedly from the cos 4 value, even after accounting for
vignetting. This can be caused by pupil distortion and image distortion.
Many super-wide angle lenses, especialy ones for 35 mm cameras, are
designed so that the aperture (pupil) appears larger as you move off axis.
This allows more light to reach the corners of the film. Likewise, extreme
barrel distortion (think fish-eye) increases the intensity near the edge of
the image.
Yet another way to cheat on the cos 4 fall-off is to use curved film.
Classical Schmidt cameras (telescopes) use have a curved film plane that
eliminates #4 and #5 above, so that the light falls off only linearly with
cos.
------------
That said I've never been bothered by the slight fall off my 90mm has on 4X5
but some people are..
--
Stacey
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Center filter? Nah, use a *fan* instead!
Date: 25 Nov 2003
David Nebenzahl nobody@but.us.chickens wrote
> Ran across this lens for auction on that little-known on-line auction site:
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item;=2966926413&category;=30077
>
> (It's a 75mm Hypergon Anastigmat.)
>
> Notice the *fan* which can be swung in place over the center of the lens.
> That's right, a fan. Guess the idea is this spins in the breeze, or you blow
> on it if there's no wind, and the vanes make a variable-density pattern that's
> darker in the center.
>
> Weird! But a kewl idea; maybe this could be revived for one's Super Angulons, etc.
>
> Plus, check out the price: up to $787 now and the seller's reserve hasn't even
> been hit yet!
The Goerz Hypergon is an interesting lens. It was designed by Emile
von Hoegh, the fellow who also designed the Dagor and Celor lenses. It
is a two element meniscus which covers about 120 degrees.
The "fan" is for evening out the exposure. Most lenses have a fall
off of illumination proportional to cos^4 theta where theta is the
image angle from the center. This is pretty severe for such a wide
angle. Because the technology for making center filters did not exist
when this lens was first made the "fan" was used to regulate relative
exposure. It works by means of an air fitting. The operation depends
on the fact that the working f/stop of the Hypergon is very small,
around f/45 and exposures with the film available at the time were
very long. When ready to make the expoure the "fan" is pushed up in
front of the lens and latched. It is then operated by means of an air
hose and bulb. The bulb spins it and after it slows down it falls away
from the lens. The normal technique is to make about half the exposure
through the fan and the other half without it. Hypergons are sometimes
found without the fan.
I don't know how rare Hypergons are, they are certainly not very
common, probably because they were quite expensive originally. The two
elements of the Hypergon are steeply curved and very thin so they are
hard to make. There must have been a relatively large rejection rate.
While these lenses are neither ansastigmats or even chromatically
corrected they still produce very good images mainly because they are
used at such small stops.
Later very wide angle lenses, mostly for aerial survey work, are
related to this lens although they are also considered double-Gauss
types. The Zeiss Topogon and similar Bausch & Lomb Metrogon can be
seen as elaborations of the Hypergon with additional elements to
provide correction for color and astigmatism.
Richard Knoppow
dickburk@ix.netcom.com
Los Angeles, CA, USA
From: "Gregory N. Latiak" glatiak@tekstrat.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Does anyone here own and/or use a center filter?
Date: Sun, 14 Sep 2003
I create the effect of a center filter using Photoshop rather than at
exposure time. This is necessary with most images taken with my 65mm
SuperAngulon f8, and sometimes with my 75mm Grandagon-N f5.6 when using
reversal film. Corner falloff is much less apparent with negative film, so
the inevitable loss of detail is generally acceptable. Corners on reversal
film tend to be a bit thin -- this would be problematic if the transparency
were the end result, but not as an intermediary to printing. Falloff can add
a dramatic note to wide-format landscape images -- a matter of taste and
aesthetics to be sure.
--
Greg Latiak
glatiak@tekstrat.com
Images http://members.rogers.com/greglatiak/
From: Charles Pezeshki pezeshki@mme.wsu.edu
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Does anyone here own and/or use a center filter?
Date: Sun, 14 Sep 2003
...
Hi Dave,
I use one on my Fujinon 65mm SWD for all my landscape color shots. I find
the difference with/without very noticeable.
Chuck
http://www.wildcountry.info
From: "konabear" maurert@ameritech.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Does anyone here own and/or use a center filter?
Date: Mon, 15 Sep 2003
I have been using a center filter for my Schneider 65mm F8 Super Angulon.
It does help to smooth out the exposure, though I find that the 65mm F8 is
at its limits doing 4x5. I use the lens rarely, so getting a Heliopan
center filter for it seemed like a lower cost alternative to upgrading to a
newer 65mm or paying for a genuine Schneider center filter.
A caveat here is that my Heliopan is currently back at HP Marketing. It's
developed a case of what looks to me like glass separation around the
perimeter of the filter. I'm only guessing that the Heliopan is a
lamination of two layers of glass sandwiching a layer that was the center
graduation on it. It is my hope that HP Marketing will honor their lifetime
warranty by replacing the filter. Thanks to the organization of my wife I
still had the original receipt!
Todd
...
From: "Joseph Schutz" Nospam@none.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Does anyone here own and/or use a center filter?
Date: Sun, 14 Sep 2003
I use a center filter on the Schneider 72mm XL lens on a Technorama 617 S III.
Otherwise the pictures are very dark on the edges.
Joe
From: foto28@aol.comedy.com (Foto28)
Newsgroups: rec.photo.equipment.large-format
Date: 14 Sep 2003
Subject: Re: Does anyone here own and/or use a center filter?
>Anyone? If so, for what lens(es) and how often do you use it? For what
>types of subjects and on what materials? Any replies appreciated!
I occasionally use one with the Schneider 80XL (didn't mean to ignore the other
thread...I've been away from the NG for a few days). Landscapes exclusively.
Initially I didn't, but there have been certain times when it would have been
beneficial (lots of movement along with fairly even-toned sky or water, or
subjects that were already brighter in the center due to placement in the frame
of bright water or snow). I've since been using it on these occasions and it's
been a good addition. This is with chrome; I haven't used it with b&w; neg.
I also have a Linhof 617SIII, with which the CF is absolutely essential when
using the 90mm lens. Without one (I've tried), the symmetrical darkening of the
ends is very distracting.
===============
Danny Burk
www.dannyburk.com - fine art photography
From: "Gordon Dooley" gdooley@update.co.uk
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Question: Anyone using an 80mm Super Symmar XL, yea or nay on thecenter filter?
Date: Wed, 17 Sep 2003
For what its worth, I use the 80mm SS XL for landscapes and architecture and
find that I do need the centre filter. I spoke with Robert White's staff in
the UK before buying it and they gave the same advice as another poster -
use the lens and only buy the filter if you think you need it.
Interestingly (to me at least) I took some shots on TMX and Maco Infrared of
the same subject (including sky) and found that the falloff was MUCH more
apparent on the Maco than the TMX. However, it was the first (and last) time
I'd used the Maco film and it may have been down to bad technique rather
than anything else
Cheers
Gordon
...
From: Bob Salomon bobsalomon@mindspring.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Question: Anyone using an 80mm Super Symmar XL, yea or nay on the center filter?
Date: Sun, 14 Sep 2003
remove.david@meiland.com (David Meiland) wrote:
> but I think it's safe to say that few users of the ubiquitous 90mm
> lens have them
As the distributor of Rodenstock and Linhof as well as Wista and
Heliopan we tell users not to buy the center filter until they see if
they feel they need one after using the lens.
A great majority of buyers of 90mm lenses do buy a center filter. This
is true for people who buy the Rodenstock 90mm lenses as well as people
who buy the Linhof branded Schneider lenses that we sell.
As the Heliopan distributor we get a large number of calls from owners
of other lenses like the Nikon and Fujis for the center filters for
those lenses as well.
It may be that for the type of work that you and your friend do a
center filter is not needed with the lenses you shoot under the
conditions you shoot and of the subjects you shoot. But that does not
make it the norm.
Additionally many shooters may find they don't need the filter due to
their darkroom techniques or their lighting techniques. But that is not
applicable to everyones techniques.
--
HP Marketing Corp.
From: longnose@mse.biglobe.ne.jp (Andreas Schmidt)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Does anyone here own and/or use a center filter?
Date: 22 Sep 2003
remove.david@meiland.com (David Meiland) wrote
> Anyone? If so, for what lens(es) and how often do you use it? For what
> types of subjects and on what materials? Any replies appreciated!
I use a center filter for my Schneider Super Angulon XL 5.6/47mm,
Nikkor 4.0/65mm and sometimes on my Schneider Super Symmar XL
4.5/80mm. The latter depends on how sensitive the image is to light
fall off in the edges and how much tilt/shift I use. I'm nearly
exclusively shooting chromes.
Andreas
From: Bob Salomon bob_salomon@mindspring.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Wide Angle film illumination
Date: Sun, 11 Jan 2004
David Nebenzahl nobody@but.us.chickens wrote:
> "Let me
> sell you something that I distribute", and who has zero understanding of
> hypothetical constructs.
Let's get something very straight, so I will say it in the simplest
terms so it does not go over your head.
I did not try or offer to sell anything. I offered to send technical
descriptions to help someone understand something that he was having a
problem grasping.
If it helps further I am including below BOTH Rodenstock's AND
Schneider's descriptions regarding their CF.
Rodenstock
For critical shots (e. g. with uniformly coloured areas towards the
corners of the picture) the physically inevitable light fall-off can be
eliminated by using the neutral grey and vignetting-free Rodenstock
Center Filters available for all Apo-Grandagon and Grandagon-N lenses. A
Center Filter should always be used if the image circle of a wide angle
lens is used right up to the vicinity of the circumference.
Rodenstock center filters are neutral gray concentric graduated filters
whose density decreases from the center up to the translucent rim. The
fall in density compensates for practically all the light fall-off to
the image edge from a working stop of 16. This also produces a uniform
illumination. The exposure must be corrected by 1.5 stop. This
corresponds to a correction of the exposure time by a factor of 3.
Schneider
When working with ultra-wide-angle lenses, the falloff of illumination
towards the corners is sometimes disturbing. For this reason,
concentrically graduated Center Filters have been designed to compensate
for this vignetting.
These filters have a transparency which increases gradually from the
center to the edges of the filter where it reaches full transparency.
The transmission is independent of the wavelength of the visible
spectrum. In order to avoid overexposure and with consideration of the
exposure latitude of the film emulsions, we have not fully compensated
for the vignetting of the lens.
It must be remembered that, when working with ultra-wide-angle lenses,
one should avoid high-contrast films, underexposure, and non-uniform
field illumination as much as possible. With the consideration of these
three factors, the use of Center Filters in combination with the
Schneider Super-Angulon can open new areas of wide-angle photography in
black-and-white and color.
For maximum results and definition when using the Schneider Center
Filters, it is necessary to increase the exposure 1.5 stops. It is also
to be noted that the lens must be stopped down at least two full stops
below maximum aperture, since only then can the maximum compensating
effect of the Center Filter be achieved.
If you need more detailed information I will even mail it to you, David,
it should not be too obtuse for you.
--
From: brianc1959@aol.com (brian)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Get a life people : Was: Mamiay 7 43mm- was Camera suggestions?
Date: 1 Nov 2003
nospam@nospam.xxx (jjs) wrote
> Yes. 3" for 4x5. It's an oversize Biogon design with a disproportionally
> large rear element (4.5") compared to, for example, the 38mm Biogon and it
> sits disproportionally close to the film, too. It is a no-compromise,
> drop-dead great lens even at F4.5. (When I did the measurements and math,
> it was a bit faster than F4, but the T rating is closer to 4.5.)
>
> No fall-off, but no movements except rise and fall, either. Typical
> fall-off will occur around 6.5"
I've analyzed literally hundreds of Biogon type lenses, and all of
them have more than one stop of falloff by the time you get to 45
degrees semi-field angle. Having a large element near the image plane
wouldn't help much unless it had positive power, which would take it
out of the Biogon category. I'm always prepared for new information,
however, and would be curious to know more about the lens you are
discussing.
One thing to remember is that ordinary human vision is very poor in
detecting falloff in a single negative or print so long as the falloff
is fairly steady. In fact, burning in the edges is often desirable
even when a wide angle lens was used. On the other hand if you put
images side-by-side as in a video projection array or a stitched image
the effects of falloff suddenly become much more dramatic.
Brian
www.caldwellphotographic.com
From: "L. Songer" sales@coatoptics.com
Newsgroups: sci.optics
Subject: Re: Graded Filter
Date: Wed, 03 Mar 2004
"Siv" psivasamy@hotmail.com wrote
> Hi Experts:
> I need to buy some graded filter to even out my illumination, where can
> I get it?
Try http://www.reynardcorp.com they've been making graded neutral density
filters for over 20 years, and are pretty good at it.
They can make them graded linearly in transmission or in density.
> Human perception is not linear; what is the relationship? Is there any
> theory releted to this topic?
Human perception is logarithmic (linear with density, not transmission).
Ask the people at Reynard. They know all about the subject.
>
> Thanks in advance for your help.
> VT
From: JK junk@mailzone.com
Newsgroups: sci.optics
Subject: Re: Graded Filter
Date: Wed, 03 Mar 2004
Siv psivasamy@hotmail.com wrote:
>Hi Experts:
>I need to buy some graded filter to even out my illumination, where can
>I get it?
>
>Human perception is not linear; what is the relationship? Is there any
>theory releted to this topic?
You can have it made here:
http://www.delta.dk/services/consulting/optical-filters/default.htm
If your application is common, they might have some on stock.
I know that exactly mathing the eye-curve is their first common
application to graded-index-filters.
They have about ten years experience with graded-index and over 30
years with interference filters.
best regards
John Knuhtsen
From: "Gregory N. Latiak" glatiak@tekstrat.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Wide Angle film illumination
Date: Thu, 08 Jan 2004
Light falloff seems to depend as much on the lens design as on the focal
length. A text on photographic optics would help to understand what is going
on -- or study your lenses and observe whether the diaphram is occluded by
the lens barrel towards the corners.
I work with 3 wide lenses on a 4x5 Technika V. The 65mm f8 SuperAngulon is
great for very wide shots, but the illumination falloff is very noticible.
One could use a center filter to correct this (I think you lose 2 stops). I
munge it in Photoshop with a circular gradient. Need to use a wide angle
focu$ing mount in this camera. My 75mm f4.5 Grandagon is a very heavy chunk
of glass, but it is brilliant and very good right out to the corners -- a
bit of a pain to use on the Technika V. The images are very close to what I
get with a 10" process lens for sharpness and color. The 90mm f6.8 Angulon
is soft in the corners wide open, down to f11. Beyond that it is quite even.
Not unreasonable for a very small, light press lens.
--
Greg Latiak
glatiak@tekstrat.com
Images http://members.rogers.com/greglatiak/
From: Roger Williams [roger@despammed.com]
Sent: Tue 2/17/2004
To: Lenses@topica.com
Subject: Re: [despammed] RE: [LENSES] Xpan 45mm vs CV50/3.5
Joe Polizzi polizzi@westbend.net wrote:
> I just thought of something, Roger. I see these specially made center
> filters for various lenses (including the XPan 45mm, right?) that are
> supposed to compensate for this fall-off; but if the falloff improves
> with smaller apertures, then doesn't the filter correct optimally at only
> ONE aperture (wide-open, I suppose), then OVER-correct as you stop down
> from there??
That must be true, Joe, and I admit it hadn't occurred to me.
I have not found my usual standby, the software radial-density filter that
comes with Dersch's PanoTools, to be completely satisfactory. It does boost
brightness around the periphery, but with no compensating adjustment of
contrast, saturation of colours, etc. After fairly thorough testing of the
Power Retouche plug-ins for PhotoShop and PaintShop Pro, etc., I think its
system of radial compensation is far superior. It even works for some kinds
of uneven illumination by electronic flash, if you're into that kind of
thing (I know you are, Joe; you know I'm not). Its lens correction plug-in
is also unusual in providing corrections for panoramas (very helpful for
yours truly).
I recommend Power Retouche plug-ins. Visit www.powerretouche.com to see for
yourself.
As the complete set of these plug-ins, including some I cannot imagine
using, is considerably cheaper than one center filter for my 45mm lens, I
am thinking of getting the set. Not this month, though... I'm already over
my allowance.
Roger
From: Joe Polizzi [polizzi@westbend.net]
Sent: Tue 2/17/2004
To: Lenses@topica.com
Subject: RE: [LENSES] Xpan 45mm vs CV50/3.5
I just thought of something, Roger. I see these specially made center
filters for various lenses (including the XPan 45mm, right?) that are
supposed to compensate for this fall-off; but if the falloff improves
with smaller apertures, then doesn't the filter correct optimally at
only ONE aperture (wide-open, I suppose), then OVER-correct as you stop
down from there??
Joe
...
From: Roger Williams [roger@despammed.com]
Sent: Tue 2/17/2004
To: Lenses@topica.com
Subject: RE: [LENSES] Xpan 45mm vs CV50/3.5
Sorry, Dingo, I missed this one.
They are similar in both being truly great lenses. The Fujinon, of
course, is an MF lens, with an image circle at least 65mm across, which
makes it very unusual and not strictly comparable with the Heliar. I
find it a little "harder" in tone than the Heliar, and it gives
excellent detail in its main application, panoramas. Colour balance is
neutral and contrast high. It does suffer Cosin-law fall-off at the
edges of the image, enough to be quite noticeable and need correction at
full aperture. The Heliar is the "softer" lens, although that doesn't
mean it isn't sharp (it is! very much so)... it's hard to describe.
"Smooth" is the best word for it that I've come across. It's very kind
to faces and skin, so I love it for the occasional portrait. (I don't
take many portraits, or I'd use it a lot more). Both have very pleasant
out-of-focus characteristics. "Bokeh" for want of a better word.
Hope this helps.
Roger
Dingo Lee wrote:
>
> Roger and friends,
>
> Hi, just came back from Bangkok, took a few shots with the Xpan 45mm,
> and found it a great lens, both in resolution and color rendition.
> Roger, you got both the Xpan 45 and the CV 50/3.5, both got very high
> ratings in many aspects, did you ever make any comparison between them ?
>
> Or does it worth to make such comparison in the first place ?
>
> Dingo Lee
From: brianc1959@aol.com (brian)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: a humbler and new question
Date: 10 Jul 2004
"jjs" nospam@please.xxx wrote
> Any thoughts on how a person could make his own graduated filters? I mean
> the physical thing itself, not a photoshop filter application (which I have
> already.)
A true graduated filter would be a real challenge to make, unless you
have a vacuum coating facility at home. A good possibility for a
home-built filter is the little-known "butterfly filter" dating all
the way back to the 1850's:
http://caldwellphotographic.com/Butterfly.jpg
This consists of a normal aperture stop followed by a central
obscuration spaced a short distance away. The central obscuration
will block on-axis rays more than off axis, and for extreme off-axis
rays it has no effect at all. Drawbacks are that it may ruin bokeh if
you have any blurred areas in your image, and also that it only works
well for one aperture ratio. The only reference I've ever seen to a
butterfly filter is an old German book by Merte and von Rohr (both
connected to Zeiss) which was translated into English by the U.S.
military after WWII. The link above shows a snapshot I took from this
book One of these days I'll put up a PDF of this classic on my
website, along with the equally classic "Zeiss Index".
Another possibility is to use a spinning fan filter like the one used
on the Hypergon. The drawback here is that you need a very long
exposure to be able to swing the filter in place.
Brian
www.caldwellphotographic.com
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