- Additive Colour
- A colourspace in which light is added to black to achieve a colour and tone. RGB is an additive colour system in which Red Green and Blue light are combined to make white.
- Alpha Channel
- is a mask channel in addition to the three Red Green & Blue image channels that can be used to isolate a particular area of an image in order for the computer to perform operations on that particular area. Alpha channels are used to describe silhouettes that have soft edges. (see: Clipping Path)
- angle of view
- Most compact cameras and SLRs use 35mm film. Slightly bigger than APS film 35mm film will allow you to make bigger enlargements from your negatives before grain becomes apparent. The 35mm film format offers the widest choice of film types and you can buy and have it developed almost anywhere in the world.
- aperture
- The aperture is the adjustable opening inside your camera lens that lets light pass onto your film or in a digital camera onto the CCD sensor. Like the pupil in your eye bigger apertures let in more light when it's dark and smaller apertures let in less light when it is bright. Aperture values are described in f numbers.
- APS cameras
- Advanced Photo System cameras give you the choice of three different print formats even on the same roll of film. APS film comes in easy to use cassettes. You drop them into the film loading compartment and they load and rewind automatically. Your negatives are returned to you in the cassette after processing.
- Array Camera
- a digital camera that uses a large CCD chip (an array of rows and columns of light sensitive pixels) to sense the entire image at one time as opposed to scanning the image one row of pixels at a time.
- Artifact
- any artificial glitch or blemish inadvertently created in or by the digital process.
- autoflash
- Many cameras have autoflash so you don't have to keep turning your flash on and off. When selected autoflash fires your flash if there's not enough natural light in your picture.
- autofocus
- Autofocus cameras take the guesswork out of focusing so you don't have to twist the lens and hope. Many cameras autofocus on what is in the centre of your frame which can sometimes cause a problem if the subject of your picture is off-centre. Most good autofocus cameras allow you to pre-focus on subjects that are slightly off-centre. To do this point the lens at your main subject and lightly press the shutter release button halfway to 'lock' the focus before recomposing the picture and fully depressing the shutter release.
