HP Designjet Z3100 Photo Printer series - Manual (Page 66)

1. All colors
2. Computer monitor gamut
3. CMYK press gamut
Finally, there are some color spaces that are not device-dependent, but instead represent how a viewer
sees colors, such as CIE Lab or CIECAM02 defined by the CIE (Commission Internationale de
l’Éclairage). The advantage of these spaces is that, unlike CMYK or RGB, if two objects have the same
CIE Lab values then they will look the same when viewed under the same conditions. Values in these
spaces can be obtained from measuring the light emitted or reflected by an object.
The solution: color management
There are many colors from an RGB-controlled device that can no be reproduced in a CMYK-controlled
device and vice versa. These colors are called “out-of-gamut” colors. The industry uses two steps to
reduce color differences as much as possible:
● Describe the color behavior of each device as accurately as possible
● Convert one color gamut to another as effectively as possible
The solution:
1. Describe the color behavior of a device as accurately as possible using an ICC profile. By
taking various RGB or CMYK combinations, sending them to a device, measuring the resulting
output and expressing it in a device-independent color space (e.g. CIE Lab), the color behavior of
a device can be described. The resulting relationship is stored in an ICC profile, which is a standard
file that acts as a dictionary to translate the device’s color space (CMYK or RGB) to a device-
independent color space (e.g. CIE Lab). The process of generating an ICC profile is called profiling.
2. Convert colors as effectively as possible using a Color Management System (CMS). A CMS
is software that uses information from ICC profiles to transform one device’s color space (defined
by a source profile) into the color space of another device (defined by a destination profile). The
difficult part of the job is with those colors that exist in one device’s gamut but not in the other. We
will explore this in more detail later on.
Briefly, we can describe any CMS by the following 4 settings:
56 Chapter 6 Color management ENWW
Color management