HP Indigo press 3050 User Manual page 77

Machine LUT for substrates
Different substrates have different characteristics which influence print quality and color
consistency (transfer, dot gain, gloss, and so on). Every substrate will have its own
machine LUT, which is saved in the substrate data file.
If you don't want to perform a machine LUT for all your substrates, it is possible to assign
a LUT from one substrate to another. The substrate data file is saved on the hard disk.
By default, the substrate will be configured to take the LUT from its own parameters. If a
LUT was not assigned to take a LUT from another substrate, it will take the default
machine LUT defined in the ink files (default LUT).
Note When creating a new substrate, remember to perform the machine LUT for it, or assign it a
machine LUT from another substrate.
Optical Density of substrates
The optical density varies between substrates even when using the same press
parameters (such as laser power and developer voltage).
A densitometer gives a lower reading on matte substrates, compared to glossy
substrates, even though it appears the same to the human eye. Therefore, the press
should adjust to a lower density on a matte substrate than on a glossy substrate.
It is possible to define the optical density for each substrate by selecting the correct
substrate gloss level:
The press will calibrate the solid density according to the following table:
Substrate gloss level
Matte (0 < gloss < 12)
Semi-gloss (12 < gloss < 25)
Glossy (gloss > 25)
HP Indigo Ink Mixing System inks will calibrate the optical density specified in the HP
Indigo Ink Mixing System file.
If you are not sure what substrate gloss level to define for a specific substrate, perform the
following steps:
1
2
3
If the color adjustment fails when adjusting the 100 percent optical density values, there is
probably a problem with the substrate gloss level definition.
76 Chapter 6 Operating the press
Matte (0 < gloss < 12) – represents a group of uncoated and highly-matted
substrates
Semi-gloss (12 < gloss < 25) – represents a group of high-quality matte and silk
substrates
Glossy (gloss > 25) – represents all glossy substrates
Perform a color adjustment on a glossy substrate.
Print a solid color on the tested substrate, and measure the solid optical density.
Define the substrate gloss level according to the table above.
Yellow Magenta
0.9 1.1
1.0 1.3
1.1 1.45
Cyan Black
1.1 1.2
1.3 1.5
1.45 1.75
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