wavelengths of RGB that most color photographic papers respond to best are the wavelengths that are passed by Kodak Wratten filters
Tricolor Separation Printing
The original color printers, as well as the recommended printing method for Type “C” papers, used the additive filters. Three exposures were made using WR98,WR99 and WR70 (alternatively 29) filters. Kodak and Fuji have since improved color separation between the Type C (RA4) color layers. Additive printing was essential to take out the ‘pumpkin’ yellows. The tricolor method kept the yellows clearer.

- The Reproduction of Color, Hunt 5th Ed. p.177-192.
- The Color Gamut Obtainable by the Combination of Subtractive Color Dyes. Optimum Absorption Bands as Defined by NonlinearOptimizationTechnique, J.ImagingScience, 30,9–12; by N. Ohta.
- Brightness and Hue of Present Day Dyes in Relation to Colour Photography, by ME Clarkson and T. Vickerstaf, PhotoJ.88b,26(1948).