CMYK color model

The CMYK color model is a subtractive color model, based on the CMY color model, used in color printing. CMYK refers to the four inks used in printing: cyan, magenta, yellow, and key (black).

The CMYK model is subtractive. It means that it subtracts or masks colors from white background of the paper. The ink reduces the reflected light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

White is the natural color of the paper, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of pure mix of cyan, magenta, and yellow.

 Using black ink 

The "black" produced by mixing usual cyan, magenta, and yellow inks is actually a dark grey color. So, modern four-color printing uses black ink in addition to the subtractive primary colors. Common reasons for using black ink include:
 Text is typically printed in black and includes fine detail, difficult to reproduce with a mix of three inks.
 A combination of 100% cyan, magenta, and yellow inks soaks the paper with ink, making it slower to dry.
 Although a combination of 100% cyan, magenta, and yellow inks should, in theory, produce a perfect black, practical inks cannot do it and the result is actually a dark muddy color that does not quite appear black. 
 Using black ink is less expensive than using the corresponding amounts of colored inks.

 Related pages 
 CMY color model
 RGB color model
 Color model

 References 

 Other websites 

XCmyk – CMYK to RGB Calculator with source code
 Color Space Fundamentals– animated illustration of RGB vs. CMYK

Category:Color models
Category:Printing
Category:Photography