Adding filters to camera lenses can create a different dimension because they can remove a predictable amount of light from the spectrum. This can be an important consideration if you're using film manufactured for sunlight shooting conditions in an indoor set that's artificially lit. There is a wide range of filters that you can choose from, depending on the onscreen atmosphere you're striving to create.
Types of Filters
Filters are designed to produce or reduce a number of effects during shooting. Filters can be adjusted to accommodate for shooting indoors with outdoor film, and to reduce the brightness and atmosphere of outdoor shots. They can also be used to create specific color effects, or to change the overall tint of images.
What do you use if you have too much natural light?
For outdoor scenes with too much natural light, neutral density filters are often used to help reduce the amount of light that's allowed to travel into the camera. Neutral density filters have little effect on color, and can be used without concern for color shifting onto the film.
For shooting outdoor scenes with a significant amount of haze or smog, skylight filters are often used to help counteract the haze. These filters can be either slightly pink or yellowish in appearance. Because they have virtually no unpleasant effect on images shot outdoors, they're often left on the camera lens in all outdoor settings as added protection to the actual surface of the lens.
Graduated filters are partially neutral density filters and partially clear. The neutral density half of the filter is positioned to reduce the harshness of the sky on a bright day without affecting the ground-level action. You can use graduated filters in the same way to create the illusion of a night sky while shooting in broad daylight.
Polarizing filters are designed to selectively remove excessive light. By rotating a polarizing filter, reflections from window surfaces and the surface of water can be greatly reduced and sometimes entirely eliminated. Care must be taken to ensure that the filter doesn't also completely remove the appearance of the window or water.
If you're attempting to reduce harshness and hard lines, you'll want to use a diffusion filter, which gives your image a soft, dreamlike quality. Diffusion filters are often used when shooting digitally, and help negate the inherent overly sharpened and often jagged edges of digital images. Color compensation filters are used to specifically alter the color of the imagery onto film. If, for example, you want your film to have a warm sepia tone, you'd use one of these filters. The eerie effects of fluorescent lighting can also be corrected with color compensation filters.
Matte boxes are square framed boxes that are fitted around the camera lens. They're designed to hold lens filters and prevent light leakage. Filters can easily be slipped into matte boxes in specially sized slots. In the case of polarized filters, the filter slot is designed so that the filter can be rotated to achieve the best polarizing effect for the lens.