The one filter that you absolutely, positively need in your bag is the circular polarizer. A polarizer is a filter that polarizes the light going through it to noticeably darken blue skies, reduce reflections and increase color saturation in your photos. The “circular” in its name means your auto focus and auto exposure systems won’t be affected by the polarized light and will focus and meter normally. Regular, non-circular polarizers are a little cheaper but won’t offer this extremely useful feature.
Polarizers are two pieces of polarized, coated glass that rotate relative to each other to increase or decrease the polarizing effect. Depending upon how much you rotate the filter, the effect can be subtle or quite dramatic.
Non-polarized, left, polarizer at max, right. Note saturated trees, sky at right.
The standard filter minuses apply here. Circular polarizers are expensive and will put two, not one additional layer of glass between you and your subject. (If you remember my earlier post about filters, you’ll remember that anytime you put glass in front of your camera, it causes some degree of image degradation.) Oh, and they’ll cost you at least one f-stop in exposure…depending on how much polarizing you do (i.e. if your base exposure is f/8, you’ll need to shoot at f/5.6 or thereabouts with a polarizer). Add to the pluses the added saturation, reflection control and the ability to double as a neutral density filter.
I think the pros outweigh the cons when it comes to polarizing filters.
Using a polarizer is simple, just rotate the filter as you look through the viewfinder. When you see the amount of sky darkening/saturation/reflection elimination you like, make the picture. Understand that if you change your camera’s orientation to the subject (i.e. change from a horizontal to vertical shot), you’ll need to re-adjust your polarizer.
I picked up a trick long ago that helps me quickly see where the maximum amount of polarization will take place. You simply make an “L” with your thumb and index finger, point your index finger at the sun and pretend your thumb is tracing an imaginary line across the sky. With that line in mind, the area of sky on the shadow side of your thumb will get the most benefit from the polarizer. A subject in front of that line will not see any benefit from a polarizer.
Hopefully, this photo shows the area of maximum effect.
So, if you’re still unconvinced about the value of a polarizing filter, borrow one from another photographer (that’s another benefit of attending photo walks…well-equipped photogs!) and give it a few turns (literally). I think you’ll see why I made room in my camera bag for this “must-have” filter.
Buy one.
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