Polarizing Filters – You can’t mimic these in Photoshop!
A polarizing filter is one of the few filters that is equally effective with color imaging and with black-and-white. It can:
• Minimize or eliminate reflections in glass, water or most any surface except metal.
• Darken skies in color photos as well as in black-and-white
• Cut through haze
• Increase the saturation of colors
Types: There are two basic types of polarizer, the original “linear” polarizer and the comparatively new “circular” polarizer. They essentially accomplish the same thing, but linear polarizers pose problems with most modern through-the-lens metering systems, so circular polarizers were developed to minimize or eliminate metering issues.
Filter Factor: Most filter manufacturers list polarizers as having a variable filter factor, usually 2 to 4 depending on the effect of the polarization. I personally just use a factor of 2.5 (1.3 stop correction) because any further darkening, say, of a sky is an effect I want, and do not want to override.
Use: The great thing about using a polarizer is that you can actually see the effect before taking the picture. When held up to the eye or placed on a lens and rotated in a clockwise or counter-clockwise direction, you can see gradual lightening or darkening as you rotate. You can pick just the degree of effect you want. At its lightest orientation, it is essentially just a 1.3-stop neutral density filter. If you are using aa non-through-the-lens camera (rangefinder, Holga, etc) you will need to hold the filter up to your eye and note what part of the filter is at “12 o’clock” for the effect you want, then put the filter on your lens in the same orientation.
Above, a polarizer effectively eliminating reflections in glass. Note that the reflections in the polished table are only moderately affected – that light was polarized in a different direction. Below, note how the polarizer has darkened the sky, increased saturation in the colors and reduced haze.
Using Polarizers with Wide Angle Lenses: Polarizers work by darkening light in the subject that is already polarized. If there is no polarized light, the filter has no effect other than neutral density. The light in a sky is not evenly polarized, so if you are using a wide-angle lens, you will capture part of the sky that may be highly polarized AND also include part of a sky that is less polarized. If you are using a wide-angle lens on a subject that does not include sky, you may not notice any odd effect.
In the end, no well equipped camera case should be without the versatile polarizing filter!