Modern digital cameras are capable of transforming almost any scene from ordinary to extraordinary. With the right tools and the right knowledge, you can actually create an image that is even more impressive than the scene you saw with your naked eye. Your camera's settings are designed to help you achieve this, as are software packages such as Photoshop Elements. You can also use any of dozens of little tools and tricks to add that little bit of interest to your image that can go a long way towards transforming your photos from plain to amazing.
One of the most important of these tools is the circular polarizer. A circular polarizer is a screw-on filter that could almost be described as a pair of sunglasses for your lens.
What is a polarization?
To understand how a polarizer works, it helps to first understand a little bit about how light works. Light is comprised of two sets of oscillating waves - electric and magnetic - that are oriented at right angles to each other. Unpolarized light is chaotic, because the light waves come from electric charges that vibrate on more than one plane. Polarized light, on the other hand, travels in a single, predictable direction.
Um, OK ... so why is polarization useful?
In simple terms, a polarizing filter simply blocks light that is reflected towards your lens at certain angles. This is useful because it can cut back on glare, make colors more vibrant and reduce the appearance of haze.
A polarizer works best when your subject is oriented at 90 degrees to wherever the sun is. To get a general idea of where in the frame polarization will be the most effective, you can use your index finger to point at the sun, and then stick your thumb out (think of the finger guns of your childhood), rotating your wrist as needed while keeping your finger pointed at the sun. Wherever your thumb is pointing is the part of the frame where the polarizing filter will have the maximum effect.
A circular polarizer has two rings. To use it, twist the front ring and watch what happens to the scene. The rotation blocks specific light waves from entering your lens, which in turn will remove reflections or darken the brighter parts of the scene. When you can no longer see the reflections in water or on other surfaces, you will know the filter is doing its job.
When to use a polarizer
A polarizer can be used to darken a cloudless sky, or to make a cloudy sky more dramatic, but depending on who you ask this may or may not be the best use for one. If you're using a wide-angle lens, a polarizer may create an uneven sky, or a sky where one part is light and the other is dark. The desirability of this effect is subjective, of course. Some photographers believe this unrealistic quality can make for a more interesting photo; others just dislike it altogether and argue that the sky can be much more easily and effectively darkened in post-processing.
Perhaps the most dramatic use of a polarizer is in removing reflections - something that cannot be easily done in post-processing. This is particularly useful if you take a lot of outdoor photos, and if water is a favorite subject. If you don't already use a polarizer in such situations, you are probably familiar with the frustration of trying to photograph the highly reflective surface of a lake or other body of water. Shooting through the surface at the rocks and/or wildlife just below the surface is next to impossible without a polarizing filter. With one, however, you can eliminate reflections and effectively capture details below the surface - or just get a better overall shot that does not include the distraction of surface reflections.
Polarizing filters can also be useful for shooting through glass. Have you ever taken a photo through a window and then been disappointed by how obvious it is that the scene was shot through a window? A circular polarizer will eliminate the reflections that are commonly present on glass surfaces, and, depending on how clean the window is of course, make it next to impossible for your viewer to tell that there was a window between you and your subject.
Polarizers also work to increase color saturation in an image. This is a side effect of the filter's ability to reduce glare and reflection - the light that is left over after those reflections are gone is diffuse, which deepens color throughout the image.
Finally, a polarizer can be used to reduce haze, which is especially common in long shots, that is, in photos that have a distant subject such as a city skyline or mountain range.
Limitations of circular polarizers
There are a few things to keep in mind when using a circular polarizer. The first is that you can't always get the desired effect from one - your results will vary depending on where the light is coming from and on the location of your subject. Sadly, you can't always move your subject to take full advantage of your polarizing filter, so in certain circumstances you may just have to shoot without one.
Second, a polarizing filter is, by its nature, a tool for reducing the amount of light that reaches your camera's sensor. This means that you may lose two or three f-stops of light, which also means of course that you'll have to compensate with a slower shutter speed or possibly a tripod (which is never a bad thing when shooting landscapes anyway).
Photography doesn't necessarily have to be about capturing reality, and every scene doesn't necessarily have to be reproduced exactly as it appears to the naked eye. A polarizing filter can help add interest to a scene that may be lacking in that certain quality that separates a good photo from a great one. Adding a polarizer to your arsenal of photographic tools will ensure that you can give your photos that extra edge when the situation calls for it.
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