There are glass, acrylic and gelatin filters. Glass filter is the most popular and convenience to use, with slight degrading of image quality, it is not recommended to use more than one together due to the repeated refraction among surfaces. Acrylic filters have a higher degrading of image quality, we must consider its influence for important work. Gelatin filters are much thinner and the degrading effect is neglectable and suitable to have two to three together. But it is not easy to clean that requiring special care.

General use filters are classified into Color Compensating, Polarizing, Neutral Density, Contrast (for B/W) and Special Effect.

Color Compensating Filter: 1A, 1B, 81A are used to lower the color temperature by 200, 400 and 600 degree Kelvin. 82A is used to raise the color temperature by 600 degree Kelvin.

PL is used to eliminate polarized light. There is linear and circular design. Circular PL is the best.

Contrast Filters is used for B/W, lightening its color and darkening the others, e.g. yellow filter will make all yellow object into white and blue color into black.

ND (Neutral Density) is used to lower the intensity of light passing through. There are 2X, 4X, 8X, X400 in glass type filter with 1 to 3 and 9 stops effects respectively. Gelatin filter type uses density as unit, e.g. 0.1, 0.2, 0.3, 1.0, 2.0 etc. Each 0.3 density is equivalent to one stop. The effect of ND filter is selective, stronger for highlight which make it a good choice to lower the contrast.

Special Effect Filter includes Cross filter (single cross, double cross, snow flake) creates streaks on highlight; Spectrum filter creates rainbow on highlight; Prism filter creates multiple images; Graduate Filter creates partial coloring effect; Soft Filter creates soften image.

There are other types of filters for various application. Since they are not for general photography, it is not listed here. Refer to the information from Kodak if needed.