Whate exactly is a \"Filter\"?

[Braveheart]

Is it like an add on lens to your camera?

From what I understand, it's purpose is to protect the lens right?

[ken-w]

Braveheart wrote:
Is it like an add on lens to your camera?

From what I understand, it's purpose is to protect the lens right?

A filter is usually just a single thin piece of glass so it is not the same as a lens.

In the days of film SLR most people kept a filter that slightly filtered UV light (a skylight or 1A filter) on their camera as a lens protector (better to scratch a $20 filter than a $500 lens). With many digital cameras such as the G1/G2 it is a bit more difficult to do this since it would mean keeping the filter tube (the extension tube that allows for the placement of filters and teleconverters in front of the lens) on at all times. Some people do this in order to protect the lens.

However, the main purpose of a filter is to change the aspect of the light coming into the camera. An example of this is a polarizing filter that polarizes the light coming into the camera, removing sun scatter and glare. Another example would be an infrared filter that lets in light only above a certain wavelength. These filters create effects in the picture that cannot be duplicated (well) by post processing software.

Other filters people use include things like a cross-screen filter that picks up highlights on water making them into small sparkling crosses.

In the "old days" of SLRs, filters were used to compensate for the limitations of film. For instance, if shooting with daylight color film under fluorescent lights, one would place an FL filter on the camera to change the colour temp of the light coming into the camera. On a digital the white balance takes care of this. Other popular filters were things like soft focus (now easily duplicated in post processing) and spot filters (also now easily duplicated in post processing) and a yellow filter for shooting black & white.

These days with the digital I carry a skylight filter for use as a protector if I'm carring the camera out of the case, a polarizing filter and an IR filter (because I like the effect).

[Braveheart]

I see, thanks for the explanation.