ENWW
Basic concepts 97
∆
E*
94
places greater weight on variations in lightness and hue and less weight on
variations in saturation. For unsaturated colors, such as neutral greys,
∆
E*
94
is roughly
equivalent to
∆
E*.
The use of
∆
E*
94
affects ink mixing results for saturated, out-of-gamut colors. These
colors are so bright that a precise match is not possible. For these colors, it is impossible
to simultaneously match the lightness, hue, and saturation. Since the lightness and hue
are visually more important than the saturation, these two quantities should be matched
as closely as possible. The use of
∆
E*
94
ensures that the color you mix has roughly the
same lightness and hue as the target color at the expense of the saturation.
∆
E*
94
is more uniform than
∆
E*. For example, for
∆
E*, a color difference of three units
between the target and the mixed color may be satisfactory for saturated colors, but
unsatisfactory for neutral colors, for which one unit may be the maximum acceptable
difference. This problem of uniformity is corrected by
∆
E*
94
. A single criterion for
∆
E*
94
may be used for the entire color space. For example, a color difference of one unit may be
the maximum acceptable difference for the matching of both saturated and neutral colors.
Color gamut
The gamut of a printing device is the subspace of the color space that contains all the
colors that may be printed by the device. When a target color is found in the gamut of the
ink mixing system, the predicted
∆
E*
94
of the best mix versus the target color is zero.
When the target color is outside the gamut, IMS computes the best mix with the smallest
possible
∆
E*
94
. In this case, the color of the best mix is inside the envelope of the ink
mixing system gamut. The
∆
E*
94
value of the predicted best mix is therefore a measure of
the color distance of the target color from the gamut of the ink mixing system.
System file types
The IMS software creates and uses the following types of files:
z
*.mix
This file contains the IMS screen information (environment). All of the information
seen on the IMS window is contained in the mix file. You should save a mix file for
each ink that you mix.
z
*.gls
*.mtt
*.pvc
These files contain the spectrums of given substrates. They are the library of
substrates that you add and use.
These files are used and/or created when choosing the substrate type.
z
Ink definition files (see “Transferring the ink definition file to the press” on page 46):
• For a Sun computer-based press, the ink definition file is sent directly to the
HP Indigo press.
• For all other types of presses, the ink definition file is saved on a network disk drive
with the .osm extension.
Summary of Contents for IndiChrome
Page 1: ...HP IndiChrome Ink Mixing System User guide ...
Page 2: ...HP IndiChrome Ink Mixing System User guide ...
Page 7: ...6 Contents ENWW ...
Page 63: ...62 Chapter 4 General procedures ENWW ...
Page 92: ...ENWW Program updates 91 ...
Page 93: ...92 Chapter 7 Help ENWW ...
Page 103: ...EN 102 ...
