Graphics Programs Reference
In-Depth Information
Macintosh, some colors will appear a bit darker. The advantages of
gamma 2.2 outweigh this. On the Windows operating system, a TRC
gamma of 2.2 is assumed. Note that there is no difference between a
display intended for a Macintosh and a display intended for a PC. That
is, this gamma issue is part of the operating system, not the physical
display itself. A display has a native TRC, which is a characteristic of the
display itself.
White Point
The white point target for a display should be specified with a chro-
maticity coordinate (the xy component of CIE xyY; see Chapter 1).
Although it is possible to adjust color for various white points, it is prefer-
able for all displays in the pipeline to use the same white point. The white
point targets that should be most commonly used are the graphic arts
standard D50 and the sRGB white point of D65. Many packages offer the
user too many (often confusing) choices. One package may offer a choice
of 5000 K and D50. Another may offer only 5000 K. Under the hood, this
package might be treating 5000 K as D50; we don't know. The D illumi-
nant and the CCT on the blackbody curve are very close. The color science
used by the ICC is based on D illuminants; when offered the choice,
choose the D illuminant. The default white point of many CRT is close
to a CCT of 9300 K. Generally LCDs are closer to 6500 K.
Logic would dictate that since we are going to view our prints under
controlled lighting of D50, we should also set our display's white point
to D50. If our display luminance level was as bright as our viewing envi-
ronment and our paper color was perfectly neutral this would be the case.
However, in reality this is not a perfect world. It is common for photog-
raphers who calibrated their displays to D50 to find that their image
previews appear dim and a bit too yellow. There are a number of
explanations as to why this happens. For one, the white of most photo-
graphic paper is very blue when viewed under a D50 illuminant. On most
displays it is harder to achieve high luminance levels at D50. It is for these
reasons that, when working with photographic paper, calibrating to D65
may produce a better screen-to-print match. We want the white of the
monitor to look the same as the white of our light box. My suggestion is
to calibrate to a D65 white point. For those working with commercial
jobs, where the ultimate destination will be offset printing, you may find
calibrating to a D50 white point produces a better match. If you are col-
laborating with a commercial supplier such as a color printer, it is impor-
tant to use the same white point.
Luminance
Luminance is the maximum intensity of white. It's separate from the
chromaticity of white. Some packages allow users to calibrate to a spe-
cific luminance value. This is important when the goal is for multiple
