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Q & A: color filters

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Most recent answer: 10/22/2007
Q:
What do you call somthing that only lets certin colours through???
- Jamie (age 13)
Spotswood Collage, New Zealand
A:
We call these filters, or colored filters. Typically they are made of glass or plastic and are commonly used in photography. Some cameras have threaded mounts around their lenses so you can screw one of these on.

With digital photography, you can often accomplish the same thing after the fact by touching up the picture with a computer program. The advantage here is that you have freedom to change the color filtering process many times with the same image on a computer, but with film you only get one try per frame (you have to change filter and shoot again if you want to try something else).

Colors can also be separated with prisms and diffraction gratings. You need to block out the colors you don't want with a piece of material which is often called a collimator. The whole apparatus is called a spectrometer, and is often used for measuring the intensity of different-colored components of light.

Tom

(published on 10/22/2007)

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