Operation Manual

Displays and printers cannot reproduce the same colors consistently when their gamuts
don’t overlap. For example, the colors shown on a display are brighter and more saturated
than are those produced by a printer. The illustrations below show representations of
the range of color and brightness values each device is capable of displaying. If you
superimpose the printer’s gamut on the display’s gamut, some of the display’s colors fall
outside the range of the printer’s gamut. The printer is incapable of reproducing the full
range of colors in the image displayed onscreen because of the printer’s smaller gamut.
Color values that are contingent upon the ability of a device to reproduce color are known
as device dependent.
Display’s gamut Printer’s gamut
What Is a Color Space?
When compared to the full spectrum of light, the gamut of a display or printer is relatively
narrow. Because of the small gamuts of the devices, mathematical models are used to
simulate the full spectrum of light within the gamuts of the devices. These models are
known as color spaces.
Color spaces in which the interpretation of a color is not dependent on a specific device
are known as device independent. The Commission Internationale de l’Eclairage (CIE) was
established in 1931 to create standards for a series of color spaces representing the visible
spectrum. The CIE color spaces, CIE XYZ and CIE Lab, are found in ColorSync Utility. As
technology evolved, new color spaces were created for RGB and CMYK color.
Device-independent color spaces are used by ColorSync Utility, Aperture, and other color
management systems to transfer and transform color data from one device to another.
Color from one device-dependent color space, such as a display, is translated to a
device-independent color space, such as sRGB, and then translated to another
device-dependent color space, such as a printer. The independent color space acts as an
objective interpreter, ensuring that the color data is accurately passed on to the next
device.
860 Appendix A Calibrating Your Aperture System