Graphics Programs Reference
In-Depth Information
trophotometer measures the target colors. The software compares the
known color values with the measured colors, which provides the infor-
mation necessary to build an ICC output profile. There are a few stan-
dard targets for building CMYK profiles that most packages support. This
is not the case when building RGB profiles. Some software packages give
the user a myriad of options ranging from a few dozen to thousands of
patches to print and then measure. The theory is, the larger number of
patches measured, the better the accuracy of the profile.
In some cases this is true, although there is a point of diminishing
returns. Some profiles produce better results with larger patch samples
depending on the behavior of the output device. Targets with more
patches will require more pages to output and more time to measure.
Some packages supply one or two targets per color model whereas others
have patch generators, which allow a user to build a myriad of custom
targets. If a printer is well behaved, fewer patches are required to produce
a good output profile. With targets ranging from as few as 40 to as many
as 10,000 patches, I have found those targets in the 800 to 1200 patch
range usually produce good results without requiring I spend my summer
vacation in front of a Spectrophotometer. As we will see, some Spec-
trophotometers are faster and easier to use than others.
Some of the more expensive and higher end profile building packages
can produce what are known as
multicolored
profiles. That is, rather than
just being able to produce a three-channel RGB or four-channel CMYK
profile, these packages can produce as many as 10 color channel profiles.
These products usually are intended for the packaging market where
printing is often conducted with more than four colors of ink or for print-
ing what is known as
HiFi
and
Hexachrome
color (more than four color
inks on press). Both are discussed in Chapter 7.
Spectrophotometers, Colorimeters, Scanners, Oh My
The measuring instruments necessary to build printer profiles fall into
two distant technologies. One type of measuring instrument is a
Spectrophotometer, which breaks the visible spectrum into many bands
providing individual intensity values for each. A Spectrophotometer is a
device that shines an illuminant onto a sample and then measures the
spectra. As you will soon see, having spectral data from the targets we
measure provide a number of useful options when it comes time to create
a printer profile. The other type of measuring instrument is a Colorime-
ter, which uses a set of color filters to mimic the response of human
vision.
If you are serious about building quality output profiles, you want to
be measuring color with a Spectrophotometer. The bad news is these
instruments can cost significantly more money than Colorimeters. There
are a few products on the market that use the less expensive Colorime-
ter to measure color patches or expect the user to scan the color targets
