Kodak's numbered color filter system — instantly identifies temperature shift and effect. On set: grab the number, gel the light, move on.
On set, you need a quick, reliable language for color filters — and that's precisely what the Wratten system is for. Kodak established this numbering decades ago, and it still functions today as a universal reference between the cinematographer, gaffer, and colorist. Instead of vaguely saying "something warmer," you simply say "81A" or "85B" — everyone immediately knows which color shift is meant.
The filters are categorized by function: The 80 series (80A, 80B, 80C) are blue filters for artificial light on daylight film — you need these when your HMIs or spots aren't warm enough, or you're using an older film emulsion. The 81 series (81, 81A, 81B, 81C, 81D, 81EF) are subtle warming filters used to make daylight slightly more orange — perfect for a golden hour mood or to compensate for the color cast of a cloudy sky. The 82 series (82, 82A, 82B, 82C) works in reverse: blue filters in gradations for even finer-tuned corrections. Then there are special effect filters like diffusers, neutral density (ND) filters with a color cast, or polarizing filters — all with numbers.
On set, these filters are usually used as a matte box (behind the lens, in front of the sensor) or as an in-line filter (in front of the lens), depending on the camera system. With digital cameras, physical filtering has become less critical — you can adjust color temperature in the white balance — but many DoPs still swear by the optical precision and the look and feel of real glass or gelatin filters. They are indispensable, especially in photography and for film cameras.
The Wratten number is your shorthand in communication with the editor and colorist. If you document that shooting was done with an 85 filter, the colorist knows what basic shift is already present in the raw data. When shooting digitally, you don't necessarily need physical filters — but the Wratten nomenclature remains the standard code. A practical tip: Always record the exact filter designation in the script or shot notes. "Warm" is not descriptive. "81B" is an instruction.