Why must use Circular Polarizing Filter for Outdoor Photography?

Answer 1

theres no must about it, use one if you want dont use one if you dont want, circular are for digital mostly as they dont like linear polarizers.......

the filter darkens skys and removes reflections, a link example of a polarizer in action - shot on film - roughly the same effect on digi -

http://flickr.com/photos/martini2005/1841374596/

EDIT: rowlf has lost the plot there are linear and circular polarizers, look them up in a search engine sometime 1st answerer

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Answer 2

A circular polarizing filter removes glare and/or reflections from water, snow, glass, sand, and painted metal - but not from polished metal. It is also used to darken a blue sky, making white puffy clouds really stand out. It also enhances colors.

There are two types - linear and circular. The circular polarizer is used if your camera has through the lens metering and auto focus.

I've used Tiffen, Hoya and B+W circular polarizers for years.

Answer 3

Just to back up Antoni. There is such as thing as a Circular Polarizing Filter. They were invented because some cameras, digital in particular cannot focus through linear polarizing filters.

teef_au.

Answer 4

There is no such thing as a "circular polarizing" filter, just a polarizing filter. A polarizing filter is like a slotted screen, only the light waves which line up with the slots get through the screen. Light coming from the sky is polarized somewhat, so as you turn the filter you adjust which direction the light waves are which get through, which has the effect of blocking some of the sky light, which darkens the sky, and improves the contrast between ground and sky.

Edit: There is no requirement that says you MUST use a polarizer, of any kind. By no such thing as "circular" I mean the name is a misnomer. What is called a circular polarizer is actually two (or more) layered linear polarizers that are offset slightly from each other. Light does not travel in a corkscrew, which is what the name circular implies and I should have said this in the answer. In the case of layered linear polarizers, the second layer allows some of the light filtered by the first layer back into the beam, effectively allowing light at two different (or more) angles back into the beam which passes through. Multiple linear layers make the filter less selective.

Answer 5

Circular Polarisers are not just for digital cameras. You have to use them on all cameras, film and digital, which have an autofocus and through the lens metering systems. For some reason I admit I do not understand, linear polarisers interfere with those syatems.