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The Harris Shutter was described in Kodak's 7th Here's How booklet, as well as by Fran Van Wagner in How to Make and Use a Harris Shutter in the PSA Journal of June 1995 pp.14-16.

The tri-color filter system uses three colored filters of red (#25), green (#61), and blue (#38A) 3 inch square Wratten filters (cost used to be $6 each, but more nowadays!).

The concept is simple. You take three separate exposures using a camera fixed on a tripod, one exposure through each of the three filters. The objects that didn't move between your exposures look naturally colored. They got exposed with all three colors in the proper balance. But anything that moved such as water waves or clouds will vary in color, due to the different filters used at the moment of each exposure.

You can still use polarizers, star filters, and other filters just as you would without the tri-color filter exposures. Just remember to adjust your exposure accordingly, if you use a polarizer or other filter in addition to the tricolor or Harris shutter filters.

The Harris Shutter takes this process one step further. You mount the three filters, one next to the other, in a line using a long rectangular piece of cardboard. You setup a holder so you can drop or pull the three filters past the lens rapidly. At the beginning and end of the line of three filters, you have extra cardboard. The line of three filters mounted in cardboard slides down past the camera lens in a holder. This holder is mounted on the camera, usually using some sort of filter ring holder in more permanent setups.

Unfortunately, not all filters have the same stop values, as shown by the table above. One approach is to double the thickness of the one-stop filters so the two thicknesses of filter provide an equivalent two stop effect. The other approach is to put two sections of the slower (two stop) filter factor filter in the Harris shutter so you have twice the length, and hence twice the exposure. Naturally, when exposing by hand with screw-in filters or a Cokin filter style setup, you simply adjust the exposure duration as needed.

In practice, you setup your camera on a tripod, and attach the Harris Shutter. Move the filter holder to the top of the holder. The extra area of cardboard now covers the camera and blocks light from hitting the film. Next, you trigger the camera shutter to open with a cable release or self-timer for a B or T long exposure shot.

At this point, you release and drop the Harris shutter filter holder. It falls downward, moving each colored filter in turn in front of the camera. At the end of its drop, there is a stopping mechanism (e.g., a piece of cardboard that sticks out and catches on a stop mechanism at the bottom of the device). Again, there is a blank area of cardboard at the other end of the Harris Shutter.

The film sees: dark (cardboard), red, green, blue, dark (cardboard). Exposure depends on how long your particular setup takes to drop the three filters past the camera lens. With a modest weight on the bottom, most Harris Shutters tend to take about 1/30th or so of a second or a little more to drop the three filters past the lens.

Simply vary your aperture to provide the correct exposure. Naturally, some experimentation is necessary. Use slide film, and take notes. Why slide film? Because color printing machines may try to correct your test runs, making it hard to judge what's really happening. You can also vary the friction of your holder setup, the weight at the bottom, and so on to change the shutter speed of your Harris Shutter.

Advantages

The big advantage of the Harris Shutter design is that you can make a relatively fast exposure. The Harris Shutter setup is much faster than if you had simply moved each filter by hand in front of the camera. The result can be some unique photos, in which a true color fashion model stands in front of a water-fountain. Everything is correctly colored, but the flowing water and water spray, which takes on a variety of red, blue, green, yellow, and other color hues.

Since the Harris Shutter doesn't require using any multiple exposure feature (other than B or T settings), you can use it on cameras lacking such features.

Manual Tri-color Filters

If you don't have a need for speed, you can setup a Wratten filter holder or other filter holder and make a series of three exposures through each of the three colored filters. In this case, you can use the same filters mounted in 3x3 inch filter holders, or colored glass filters in standard screw-thread camera filter mounts (e.g., 52mm, series VII).

If you don't use these Wratten filters, you may have to contend with some math! In other words, if you have a 1 stop filter factor red filter, a 2 stop factor blue filter, and a 2 stop factor green filter, you can't expect to get normal colors by exposing each one equally. More red light will reach the film. The total exposure for each color should be the same. So if the red filter is only one stop versus two for the other colors, you need only half as much exposure on the red filter to equal that on the other two colors. Make sense? So you have to adjust for filter factors when exposing by hand too.

Let us say you are shooting a normal scene in full daylight that meters out at 1/125th second at f/16. You want an exposure of 1/125th in white light, right? White light is made up of red, green, and blue light. So you also want exposures of 1/125th in red, green, and blue light to get the same total exposure as if it were 1/125th in white light. Okay so far? Now both the #47 blue and the #58 green filters are two stop filter factor filters. So you need two stops more light, so you open up from 1/125th to 1/30th. Expose each filter at 1/30th to get the same amount of blue and green light as in 1/125th second of white light exposure. As for #25 red filter, it is only one stop, so you only have to use a one stop increase from 1/125th to 1/60th second. Combined together, these three filters should produce a white light equivalent exposure of 1/125th. Got it?

Unfortunately, filters vary so you have to calibrate your filters and film for each light source (e.g., daylight). You can use the above calculations as a starting point. Hold one filter constant. Vary the other two filters up and down from there in one-third or smaller f/stop offsets. Pick the combination that gives the best color result (e.g., as seen on pure white objects). If the best color slide is over or under-exposed, you will have to adjust exposures accordingly. Once you have these factors figured out, you can simply refer to a crib sheet with your notes on how to get optimal tricolor photographs.

An added complication to the above happens in the real world, because levels of light are frequently changing. If you are shooting clouds for color effects on a bright sunny day, you may not have any problems. But if the light is varying rapidly, you will have to quickly meter the scene and apply the correct filter factors so all three exposures are equivalent.

With pure red, green, and blue filters, you should be able to get a true white color without any color casts with enough experimentation. Why do you need to experiment? Because filter stop values are only approximate, and can vary widely both for individual filters and batches of gelatin, and with age and other factors. So a nominal one-stop red filter may actually be +0.82 stops or +1.21 stops in reality. Even a modest offset can cause a color cast. Examination of any CC05 color correcting filter will show how small a color tinge may be and still be noticeable!

In very long night time exposures lasting a few seconds or longer, you may run into reciprocity failure, causing a color cast. Otherwise, color shifts and casts should only be caused by object motion!

In practice, filters differ slightly, and can vary with age. So you just have to experiment with a roll of film, a tripod, and a sky with some briskly moving white clouds. Use your calculations to provide a ballpark set of exposures. Naturally, you will need a camera that can do multiple exposures relatively easily too (e.g., Nikon FE with multiple exposure control).

With these slower, manual tricolor shots, you will get a surprising variety of colors. Fixed objects should ideally come out looking natural in their coloration if the exposure ratios are correct. But your slow moving objects such as waves on a beach or clouds will be strongly colored in parts depending on which filters were used and when. Where red and green overlapped, you may get a yellow color, and so on.

Multi-color Ghosts

Jim Adams article titled Using Filters - Tricolor [in Petersen's Photographic of January 1995, pp.40-43] describes an innovative use of tricolor filter techniques. He creates color ghosts on film, much like the multiple exposure ghosts on black and white film, but with a colorful difference. His multiple exposure technique injects objects and their shadows into full color pictures, using tricolor techniques. By timing the multiple exposures so the object or its shadow appears during some but not all three filter colors, you can create various object and shadow colors.

Mr. Adams suggests a number of other special effects, achieved by moving the camera between exposures and the like, which can produce unusual and interesting effects. Read his article, and experiment away!

Multi-colored Strobe Color Effects

A related multi-colored effect is possible at night, or in the studio, using strobe or lights and colored gels. Imagine a face. Now put two lights on either side of the head, 180 degrees apart. Cover one light with a red gel, and the other with a green gel. The face will be colored red on one side, and green on the other.

But move the lights around to the side, towards an acute angle of 45 degrees more or less. Now some parts of the face are still only getting colored by the red light or the green light. But other areas are getting hit by both red and green light, producing a mixed yellowish lighting effect. The result will be to provide an unusually colored and eye-catching sculpting in color on the surface of the face. You can do the same thing with any irregularly shaped object, especially one with sculpted areas that can be used to cast interesting shadows.

Naturally, you can use any set of colors, or even multiple colors. Since you are shooting at night, you can adjust exposures so multiple exposures can be made, with multiple filters in use for multiple color effects. Wild, huh?

Painting Colors with Colored Strobes and Lights

The final trick is to paint with light, but using colored gels or filters on your strobe or light. In painting with light, you work at night or in a darkened studio. You take a flashlight or strobe, and walk around while casting light into the areas and crevices of the area you want to photography. Your camera is pointed at this scene, and set on time exposure (locking the cable release to open if needed, other cameras have a time or T setting that stays open until tripped closed again). One tip is to avoid getting your body between the camera and light you are projecting, to avoid catching your body as a silouette or profile.

You can buy these colored gel kits for strobes relatively cheaply, or make your own out of colored plastic gels. Old report covers of tinted clear plastic gel material work great for larger lights. You may have to put several layers, as the color tinting is sometimes fairly light (so you can read through them). You can also buy low cost color gel filters from various stage lighting sources, fortunately much cheaper than the same size Wratten filters!

Fun!

All of these techniques will add F_U_N!!! to your photography efforts, and give you a reason to break out your camera after the sun sets!

Enjoy!

From: dade36@aol.com (Dade 36)
Newsgroups: rec.photo.technique.misc
Subject: tri color filters
Date: 30 Oct 1998

I have been trying the technique of using tri-color filters on a triple exposure with each exposure using a different color filter, one red, one blue and one green. This supposedly makes the final image have proper colorization except for anything that moved from one exposure to the next such as clouds or water. I use E100SW film rated at 300 ASA (for the triple exposure). Then with the filter over the lens, I simply meter normally for each exposure. The overall exposure is correct, neither over nor under exposed. My problem is with the color cast of the final image.

For standardization I will name the filters using the Kodak Wratten number in the red, green, blue order. I was first told a 25, 58, and 47 series would work. This gave a very reddish overall cast. Therefore I experimented with overexposing the green and/or blue or underexposing the red, but never found an acceptable combination. Then in the B & H catalog under the Kodak filters section, it looks like two combinations would work: 29, 61, 47 or else 25, 58, 47B. I bought 3 more filters to complete each set, but again have not had success on the color of the final outcome.

I now have 6 filters (for about $150.00) but still no solution. This is getting expensive, but I know there is a combination of equal density filters that would satisfactorily suffice (it is how a TV works). Does someone there know which combination of filters would work or what I may be doing wrong? As a second question, is there a combination of magenta, yellow and cyan filters that would also work?

Any info would be greatly appreciated. Thanks.

dade36@aol.com

Date: Fri, 30 Apr 1999
From: James Fallon High d8266hn1@ozemail.com.au
To: rmonagha@post.cis.smu.edu
Subject: Tri-Colour Flash

I have been working with filtering three off-camera flash heads, each head carries the Wratten equivalent of Hoya's 'Pop' colour filter. Each flash head is set to direct at the subject at approximately sixty degrees each from subject centre on a one-eighty degree arc. A hand held light meter is used to calibrate the output by moving each head the required distance from the subject, or controlling the output electronically, to provide an identical EV. Any part of the subject which receives even illumination from the three strobes will reproduce as lit by 'white' light, without colour cast. Obviously with highly textured subjects or 'open' subjects the surface can be broken up into a myriad of the additive and subtractive triplets. Shooting a still life illuminated through a coarse metal grid just out of your angle of view, with non-diffused sources, creates thousands of refraction patterns in RGB, CMY. What the method does with light blonde coarse hair is near unbelievable. I'm sure the process has not gone undiscovered but the procedures are simple and open to broad experimentation, especially combining with daylight backgrounds out of flash range. Yep, FUN!

John Skillington
AUSTRALIA
d8266hn1@ozemail.com.au

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Broken Links:

Harris Shutter  (RIT #24.01) was at:

http://www.algonet.se/~bengtha/photo/rit.edu/FAQ24.txt (pre 2/2003)