More Ways to Modify Light
Lens filters change the way light reaches the camera lens. They can be extremely useful for achieving better color, contrast, and detail in a variety of lighting situations. Some can be used to create special effects or even out-lines and wrinkles in portrait work.
Neutral-density filters reduce light. They don't change the color of the light; instead, they darken it by one to three f-stops, depending on the filter. If you're using fast film on a sunny day and you're worried about overexposing a brightly lit subject, you can use a neutral-density filter to control the exposure and still shoot with a slow shutter speed or a wide aperture. There's also a neutral-density filter that goes from dark to light gradually. You can use this to control overly contrasting scenes by toning down the difference between dark and light areas. Again, this may be unnecessary in most cases when shooting digital. Contrast adjustment can be very easily done in image-processing programs. The exception to this may be when you are photographing a bright sky and want to ensure that highlight details are not overexposed or blown out, which can happen quite easily in digital photography.
These filters make blue skies bluer, reduce and eliminate glare and reflections, and reduce haziness in both black-and-white and color shots.
Don't wear polarized sunglasses when shooting with polarizing filters, as you won't be able to see how the image will really look. The polarized lenses in your glasses will interfere with the polarizing effect of the camera lens, making it impossible to be sure what you're seeing is correct.
Polarizing filters come in two versions. The linear type is for use on manual SLRs. Circular polarizing filters work with the focusing and metering systems on automatic SLRs. Circular filters can also be used on manual cameras, but linear filters won't work with the systems on some automatic cameras. If necessary, you can use a linear filter if you manually set the exposure to compensate for it. You would also then focus the lens manually or use autofocus before attaching the filter.
Enhancing filters are used for enriching the saturation of certain colors, including reds, rust-browns, and oranges. They're specially designed to make these colors more intense while not affecting other colors in the scene.
Primarily used when shooting with black-and-white film, these filters enhance certain colors in a scene by filtering out some colors and allowing others to pass through to the lens. Yellow filters, for example, absorb the color blue and darken the sky. They also add definition and contrast to clouds. Color filters can be used with color film to create special effects. Color-balancing filters are also used to warm up or cool down the overall colors when shooting outdoors in certain situations. There are also color-balancing filters that let you use daylight film in unusual ways, like indoors without a flash or under incandescent light. Color-balancing filters also allow you to use indoor film outdoors in sunlight.
Digital photographers can find many filters and other controls for color adjustment and enhancement in PhotoShop and similar programs. Color cast and intensity can be adjusted in most good editing software. The capacity for color-correction in these programs usually exceeds what you can achieve using filters on a film camera.
Since the colors on print film can also be corrected when the film is printed, many photographers only use color-balancing and color-enhancing filters when they're shooting slide film. However, using color filters with print film will give you more control over the colors you get on the front end, lessening the amount of correction necessary after the fact.
Star filters have etched lines on them that convert points of light into stars. Depending on the filter, the effect can be highly dramatic or finer and less obvious. They're useful for adding sparkling effects to water scenes or for calling attention to a specific aspect of an image, such as the light reflecting off a motorcycle helmet or a crystal goblet.
These filters contain a special element that scatters the light reaching the camera lens. Images taken with them are in focus, but the details are softened, hence the name. This effect is widely used in wedding and portrait photography to enhance complexions and smooth out wrinkles. They come in various strengths.
You can make your own soft focus filter by putting a nylon stocking over your lens. Petroleum jelly also creates soft effects — but put it on a clear lens filter instead of your lens. Some people even create soft images by breathing on their lenses and fogging them up.
In PhotoShop and PhotoShop Elements, the “blur” filter can give a similar effect if used with restraint by digital photographers. You will even be able to choose the amount of softening and blur to use and experiment to see what works best for your subject.