Wratten number Labeling system for optical filters
Marumi used to have various color temperature conversion filter whose name were described with a combination of numbers and a letter such as 80A, MC-85A, or 81B.
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Definition
A labeling system for optical filters, usually photographic, comprising a number sometimes followed by a letter. The number denotes the color of the filter but does not encode information directly.
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Origin
Named after Frederick Wratten, the founder of the first photography company, the system was later manufactured by Eastman Kodak and continues under Tiffen corporation
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Use in Astronomy
Commonly used in observational astronomy by amateur astronomers and in photomicrography.
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Coding Variability
Filters made by different manufacturers might carry the same Wratten number but not match the spectral definition due to differences in manufacturing techniques.
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Reduction in Digital Photography
The need for color filters, including those identified by Wratten numbers, has decreased in digital photography where color adjustments are made through firmware or software.
Wratten number example: MC-82A
MC-82A is a color temperature conversion filter. "MC" means Multi-Coated with Anti-Reflectance.
The 82A color temperature conversion filter is a cooling filter used to slightly increase the color temperature.
In analog photography, the light in the morning and evening has a lower color temperature, resulting in a reddish hue. The 82A filter is used to correct this.
Thank you for your attention!
Marumi Team
