use RGB (additive primaries) while printers use CMYK (subtractive primaries, plus black).In addition, there is a limit on how many colors a monitor or printer can generate. This is knownas a device's color gamut:Some colors can be reproduced on both devices, while others can be displayed on a monitorbut cannot be printed, or vice versa. In practice this may lead to a printed page not matching theoriginal on-screen image. What has happened?Images can be captured:y through scansy through digital photographyy through direct input via application programsBut however the original image is obtained, it will be displayed and manipulated on-screen inRGB color, then converted to CMYK for printing. Each of these processes requires dataconversion and manipulation.An image seen on a computer monitor relies on the monitor's ability to reproduce the image andrepresent colors within it. Adjustments such as brightness, color and contrast also tailor theimage to the preference of the viewer rather than a display of true color. The data sent to theprinter may not be adjusted to allow for imperfections in the toners used.These differences in monitors and printers can to a large extent be reconciled through the useof Color Management Systems.Specifying ColorThere are many ways to specify color and many models to use, including:y HSLy RGBy HSBy CMY[K]y CIE Yxyy CIELAB and CIELUVy YCCEach of these models have their advantages and disadvantages and are useful in particularsituations. We will only discuss the first two here.The HSL Model340
