Wratten number

Labeling system for optical filters Kodak Wratten filter 80A in its original packaging Wratten numbers are a labeling system for optical filters, usually for photographic use comprising a number sometimes followed by a letter. The number denotes the color of the filter and its spectral characteristics, and these numbers can be grouped into broad categories, but the numbering system is arbitrary within a group and does not encode any information. For example, within the photometric group of color correction filters, the 80A–80D are blue, while the next filters in numerical order, 81A–81EF, are orange. Letters almost always increase with increasing strength (the exception being 2B, 2A, 2C, 2E). History and use They are named for the founder of the first photography company, British inventor Frederick Wratten. Wratten and partner C.E.K. Mees sold their company to Eastman Kodak in 1912, and Kodak started manufacturing Wratten filters. They remain in production, and are sold under license through the Tiffen corporation. Wratten numbering overview No. Color / Use 0–2 Colorless 3–18 Yellows 19–29 Oranges & Reds 30–36 Magentas & Violets 37–50 Blues & Blue Greens 51–69 Green