Gum bichromate negatives of cyan, magenta, and yellow or red, green, and blue are used for a full-color image. Some photographers prefer substituting the cyan emulsion in the CMYK separations with a cyanotype layer. A simple duotone separation combining orange watercolor pigment and a cyanotype can yield surprisingly beautiful results. Low density photographic negatives of the same size as the final image are used for exposing the print. No enlarger is used, but instead, a contact printing frame or vacuum exposure frame is used with an ultraviolet light source such as a mercury vapor lamp, a common fluorescent black light, or the
Shades of blue system are the three colors of light chosen such as to provide the maximum gamut of colors that are capable of being represented on a computer or television set. This color is also called color wheel blue. It is at precisely 240 degrees on the HSV color wheel, also known as the . It is a spectral color which lies at, or near, the short-wave (violet) end of the traditional "blue" and possibly was classified as "indigo" by Newton. Its complementary color is yellow. The color defined as "blue" in the CMYK color system used in printing, also known as