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A filter is a simple to use, yet often overlooked, accessory. By absorbing its complementary (opposite) color, a filter can improve both contrast and detail in black and white photography.
RED
After climbing to the top of a mountain, a lone pine tree stood boldly before me. Behind the tree, clouds formed a magnificent backdrop, an explosion of light and shadow. Before reaching for my camera, I reached for the accessory that would bring the light out to its full potential. I pulled the red filter into my line of sight. The details of the shadows grew more defined, bringing what could have been a dull picture to life. The red filter, absorbs ultraviolet, blue-violet, blue, and green. By doing this, it lightens the yellows and reds while darkening the blues of the sky. Contrast is increased while bluish haze is filtered out. Suddenly the dull photograph jumps to life. Though the red filter made the difference to this photograph, its not always the answer. Light is always changing and no one filter can do it all. For example, a red filter would not be appropriate for low light conditions or active subjects because it blocks the light by three stops, making proper exposure difficult. Another potential problem is in the contrast. There are situations where the red filter will increase the contrast too much. In this case the light colors (red and yellow) will become too bright while the darker colors (blues and greens) will become too dark. All detail will be lost and the photograph will be a disaster. YELLOW Like the red filter, a yellow filter, which absorbs ultraviolet and blue-violet, will also increase contrast, and bring out clouds. However, the yellow filter only blocks light to one stop, and the increase in contrast is not a dramatic as the red filter. DEEP YELLOW Between the yellow and the red filers is a deep yellow filter. It blocks light to one and a third stops. It increases contrast sharper than the yellow, but not as intense as the red. SKY LIGHT / ULTRAVIOLET A sky light, or ultraviolet, filter will absorb ultraviolet light. This has little to no effect on black and white film, but is a wonderful lens protector. A chip, crack, or scratch in a lens can be quite costly, but a damaged filter is easily replaced. WHICH FILTER SHOULD YOU USE? If you're not sure which filter is right for a particular scene, simply hold a filter up and view your subject through it. When you see what you want to capture, you are holding the right filter.
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