Creating Printer Profiles with ColorGPS

Creating Printer Profiles with ColorGPS
Application Notes
Creating Printer
Profiles with ColorGPS
Creating Printer
Profiles with ColorGPS
ErgoSoft AG
Moosgrabenstr. 13
CH-8595 Altnau, Switzerland
© 2010 ErgoSoft AG, All rights reserved.
The information contained in this manual is based on information available at the time of publication and is subject to change without notice. Accuracy and completeness are not warranted or guaranteed.
No part of this manual may be reproduced or transmitted in any form or by any means, including electronic medium or machine-readable form, without the expressed written permission of ErgoSoft AG.
Brand or product names are trademarks of their respective holders.
The ErgoSoft RIP is available in different editions. Therefore the description of available features in this document
does not necessarily reflect the license details of your edition of the ErgoSoft RIP. For information on the features
included in your edition of the ErgoSoft RIPs refer to the ErgoSoft homepage or contact your dealer.
Rev. 1.1
Creating Printer Profiles with ColorGPS
i
Contents
Basics on ColorGPS ...................................................................................................................................................1
Using ColorGPS ..........................................................................................................................................................2
Starting the ColorGPS Wizard .........................................................................................................................2
The ColorGPS Wizard .........................................................................................................................................2
Basic Settings ........................................................................................................................................................2
Choosing the Print Environment ..............................................................................................................2
Creating the Profile .............................................................................................................................................3
Color Settings ..................................................................................................................................................3
Total Ink Limit ...........................................................................................................................3
Black Generation .......................................................................................................................3
Calibration Chart Presets ............................................................................................................................3
Calibration Chart ............................................................................................................................................4
Printing the Calibration Chart ...................................................................................................4
Measuring the Calibration Chart...............................................................................................4
Calculating the Profile ..................................................................................................................................6
Optional Settings .......................................................................................................................................................8
Overview of the Options ...................................................................................................................................8
Using the Options................................................................................................................................................8
Calibration Chart ............................................................................................................................................8
ICC Neutral Black ...........................................................................................................................................9
ICC Profile Accuracy ................................................................................................................................... 10
ICC Profile Contrast .................................................................................................................................... 10
ICC Profile Gamut Mapping .................................................................................................................... 11
Priorities ................................................................................................................................. 11
Color Purity ............................................................................................................................ 11
RGB Special ............................................................................................................................ 11
Color Gradients ...................................................................................................................... 12
ColorBoost Option ................................................................................................................................................. 12
Choosing the Correct GCR .................................................................................................................................. 13
No Black (GRC0) ................................................................................................................................................ 13
Black only in Shadows (GCR1) ..................................................................................................................... 13
Black in Dark Tones (GCR2)........................................................................................................................... 13
Black from middle Tones (GCR3) ................................................................................................................ 14
Black also in Light Tones (GCR4)................................................................................................................. 14
User defined Black (GCR+) ............................................................................................................................ 14
Creating Printer Profiles with ColorGPS
ii
Basics on ColorGPS
ColorGPS creates a color profile conform to the ICC standards, which characterizes the maximum gamut of the printer. The technical term for a printer’s color space is gamut.
By using an output profile created with ColorGPS you can make sure that all input files, regardless of input color space are rendered color-accurately.
More information on color management can be found in the manual part “Color Management” or in current technical literature.
The “International Color Consortium” (ICC) is a group of manufacturers that have joined
under the lead of Fogra to define the ICC format.
This format contains cross-platform specifications after which third party developers can
create profiling tools and applications to support the ICC standard. Among the founding
members of this consortium are companies such as: Adobe Systems Inc., Afga-Gevaert
N.V., Apple Computer Inc., Eastman Kodak Company, FOGRA (Honor Member), Microsoft
Corporation, Silicon Graphics Inc., Sun Microsystems Inc. and Taligent Inc. These companies have committed themselves to fully support the ICC specifications in their operating
systems and applications.
ColorGPS is an “IN-RIP” solution which can only be used as part of an ErgoSoft RIP. Such an
“IN-RIP” solution has the advantage that the profiler has direct access to data such as e.g. the
density linearization. Furthermore, data such as the calibration grid do not need to be exported and imported, but can be processed directly within the program.
To create an output profile for a printer, the print environment must already contain a density
linearization. The density linearization is the basis for the output profile. ColorGPS even offers the possibility to create output profiles using only the density linearization.
Creating Printer Profiles with ColorGPS
1
Using ColorGPS
Starting the ColorGPS Wizard
To start the wizard, click the ColorGPS icon under the Linearization & Profile Tools
list in the Print Environment toolbar or select menu Tools > Linearization & Profile
Tools > ColorGPS.
The ColorGPS Wizard
The ColorGPS Wizard is made up of two parts.
1. Basic settings
Choosing the print environment
2. Creating the profile
Color application
Calibration chart
Creating the profile
Basic Settings
Choosing the Print Environment
The first dialog window allows you to choose the print environment that will be edited. The
print environment currently active in the JobComposer is always selected by default.
Choose the print environment
that should be edited in the Print
Environment list.
1
1
Depending on the selected print
environment, the Density Linearization section will display the density
linearization used in that print environment.
2
The Used Colors section displays
3
the colors that are used in the
selected print environment. Light inks
are not shown as independent colors.
Creating Printer Profiles with ColorGPS
2
3
2
Creating the Profile
Color Settings
The Color settings section allows
you to set a maximum amount of
ink that should be used as well as how
black inks (K) should be handled.
1
Total Ink Limit
1
2
The total ink limit for the profile is
based on the total ink limit for CMYK
files without input profile, which is de3
fined in the print environment and
adapted from there. But there is also a
possibility to use different values.
5
Using the Apply Ink Limit on Top
of Printer Profile option available in
the print environment, the ink limit for
the profile can be overwritten with the one from the print environment.
Using a lower ink limit than the one the profile was created with can cause color inaccuracies. Hence this option should only be used in emergencies.
Black Generation
Using the dropdown menu Black Generation, the desired black generation can be selected.
ColorGPS will recommend the most suitable black generation mode based on the set ink
colors. You can find a more in-depth description of the different GCRs in the “Choosing the
Correct GCR” section of this manual.
Calibration Chart Presets
In the dropdown menu Precision of the calibration chart, you can define how precisely the printed chart should describe the gamut of the printer. A higher precision
leads to a higher amount of patches to be measured, but leads to better results.
2
Click the Calculate calibration chart button to create the calibration chart.
The Size of calibration chart section allows you to change the number of patches on the
calculated calibration chart. This can be helpful if e.g. you need an exact amount of patches.
An identical amount of patches combined with high precision of the calibration chart results
in more accuracy on the gray axis while the combination with lower precision of the calibration chart results in more accuracy at the edges of the gamut.
Creating Printer Profiles with ColorGPS
3
Calibration Chart
3
Section Calibration chart allows printing and measuring the calibration chart as well as
checking the measurements.
Printing the Calibration Chart
The generated calibration chart can now be printed using the Print button.
Measuring the Calibration Chart
Before starting to measure by using the Measure button, make sure that the Chart ID displayed in the dialog matches the one printed on the chart.
Now start the measuring dialog using the Measure button.
The Manage Measurements dialog gives you an overview over
the chart pages to be measured for
the current calibration. The Measured column shows how often a
page has already been measured.
3
4
To measure a page, select it
and start the measurement
with the Measure button.
4
4
The upper part of the dialog shows which
row should be measured next. Make sure
that you always measure the line that is specified.
The lower part of the dialog displays the
progress of the measurement.
As soon as all lines of the current chart page
have been measured, you can close the
measuring dialog using the OK button.
Creating Printer Profiles with ColorGPS
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The Manage Measurements dialog lets you select the next page
to be measured and repeat the
previously described steps.
We strongly recommend measuring each page several times.
The Manage Measurements dialog allows you to save measurements and to continue them at a
later time. To save a measurement, click the Save button. The program will automatically
propose the Chart-ID as a filename. We recommend using that one and maybe amend to it if
necessary.
Furthermore we recommend to also save the ColorGPS File (*.cpd file) should the measuring
process or the creation of the profile be interrupted. To complete the measurement at any
other time, you can load this measurement by clicking the Load button. Please note that
measurement that has not been saved is lost after leaving the Manage Measurements dialog. This also applies for complete measurements that are further processed after the dialog
is closed.
Also, you can select the measured
data in the lower left window to
automatically display the measurements. It is also possible to
select several measurements to
compare them.
When having selected one measurement, the expected and the
actually measured values are displayed; otherwise, only the measured values are displayed. You can access specific values by clicking on the respective
patches. Then, the value may be deleted or re-measured.
Once the measurement is completed, you can leave the Manage Measurements dialog by
clicking the OK button to calculate the average of all measurements and to get back to the
ColorGPS wizard.
In the ColorGPS dialog, you can always access all measurements using the Show Measurements button.
Creating Printer Profiles with ColorGPS
5
Calculating the Profile
After having measured the calibration chart and closed the Measure Color Chart dialog , click the Generate profile button to create the ICC profile. By default, the ICC
profile is automatically embedded into the current print environment. If the print environment is configured to use an external printer profile (or when the ICC profile is re-created
using saved ColorGPS data *.cpd and the original print environment does no longer exist)
you are prompted to specify a name and save the ICC profile.
5
Please note that this will save the generated profile but not the settings and measurements
used to create the profile. To save the settings (presets, calibration chart, measuring values,
etc.) select menu File > Save. This will save all settings in a *.cpd file.
After having created the profile, close ColorGPS by clicking the Finish or the Cancel button.
You will be prompted to save the ColorGPS data in a *.cpd file when not having saved them
already.
Creating Printer Profiles with ColorGPS
6
Optional Settings
COLORGPS
Creating Printer Profiles with ColorGPS
7
Optional Settings
ColorGPS has several options available that allow the professional to make settings for gamut mapping and color mixing. These do however require technical knowledge to be used
efficiently and precisely.
Overview of the Options
The ColorGPS menu bar allows selecting the following options. Depending on your license,
some options might not be available to you.
Calibration Chart
ICC Neutral Black
ICC Profile Accuracy
ICC Profile Contrast
ICC Profile Gamut Mapping
ICC Color Intensity (Color Boost)
Using the Options
Calibration Chart
The Calibration Chart Print Options allows you to make settings that affect the look and
output of the calibration chart.
The Geometry selection menu allows you
can change the geometry that should be
used (placement, size of the patches). ColorGPS
will suggest a fitting geometry based on the
measuring device selected in the ErgoSoft RIP.
1
The number of patches to be printed per
row can be set by using the No. of patches
per row option. Keep an eye out for the maximum amount of patches readable per Row,
which varies depending on what measuring device you use.
2
1
2
3
5
4
6
7
By default, during chart creating very similar or even equal patches are omitted in order
to reduce the number of patches to measure. In addition, the number of patches can be
reduced by reducing the quality of the calibration chart. When the option Use fixed chart
layout is checked, very similar and equal patches are not omitted and the quality of the calibration chart is unchangeably set to 100%. This might dramatically increase the number of
patches to be printed and measured. On the other hand it avoids that the quality of the cali3
Creating Printer Profiles with ColorGPS
8
bration chart is set to a too low value, especially when ColorGPS automatically creates small
charts because of the number of inks used.
When using the Edit job before printing option, a generated chart can be edited in
the ErgoSoft RIP just like every other. This option should only be used in special cases,
since the program will not automatically select the correct print environment; you will have to
make sure the right one is selected yourself. Otherwise errors will occur during calibration.
4
Option Print multiple calibration charts across job width duplicates the calibration
chart across the entire printing width, whereas every second chart is rotated by 180°.
This comes in handy at times since there are several charts available for ongoing processes
(such as sublimation) or if a chart is damaged by e.g. printing errors, so you do not have to
repeat the entire step.
5
6
If the option Print additional charts rotated 90° across job width is activated, a
second row of calibration charts will be printed that is rotated by 90° respectively by
270°.
Instead of printing a long but small job with the calibration chart, option Use multiple
columns to print chart to save media divides the long chart into several parts printed
next to each other in order to use the whole job width and thus, save media.
7
ICC Neutral Black
The option ICC Neutral Black allows selecting the method how neutral black is mixed:
Blackest Black mixes the black using as much colored
ink as possible resulting sometimes in a color shift in
the darkest black.
Darkest Neutral mixes the black regarding to the
neutrality of the black. This may result in a dark black
that is not as brilliant as the one mixed with Blackest
Black but might avoid the color shift in the darkest
black.
Creating Printer Profiles with ColorGPS
9
ICC Profile Accuracy
The option ICC Profile Accuracy provides the possibility
to set the number of calculated grid points and the accuracy of the profile.
A higher amount of grid points leads to a more precise
profile, but will also require more time to calculate. Also
it will make the file become larger.
max. gamut
- precision
1
+ precision
3
2
To further describe how the number of printed patches affects the profile, the images 1 + 2
show heavily simplified graphics of the maximum LAB gamut (outer blue line) and the device
specific CMYK gamut (inner line). In image 1, less grid points are selected than in image 2.
Hence the gamut in image 2 is described more accurately than the one in image 1 and can
therefore be used more efficiently (see image 3).
ICC Profile Contrast
The ICC-Profile Contrast option allows you to set in what areas the profile should allow textures, respectively should have high contrast.
You can increase or decrease the contrast in
terms of saturation. This results in more or less
texture in light and dark tones (respectively in
saturated or unsaturated colors).
For perceptual rendering intent and Saturation,
the brightness contrast gets adapted to the maximum black automatically, so the neutral setting
of 100% delivers the best results.
Changes to the standard settings can lead to
unexpected results.
There are no contrast settings for the colorimetric
rendering intents, since they would lose the color
correctness.
Creating Printer Profiles with ColorGPS
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When decreasing the contrast, the apparent gamut gets bigger, meaning that colors on the
outer edges of the Gamut also get textures.
ICC Profile Gamut Mapping
In this dialog you can set the parameters for the gamut mapping, meaning that you can set
how the colors that are out of gamut should be calculated. But to “apparently“ enlarge the
gamut (“apparently“ moving the gamut’s edge out further) you should set a lower contrast in
the ICC Profile Contrast option.
To “apparently” increase the gamut in this case means to give the RIP a recipe that it should
apply to imitate colors that are out of gamut.
The following four parameters are available:
Priorities
The Priorities tab lets you set the derivations
that should be tolerated, so you can define in
which part of a color recipe the RIP should accommodate to the out of gamut color. You can
set in which area of the gamut you want to accept changes or not by using values from 0 100.
Entering e.g. 0 into the Higher luminance (+L)
field means that deviations in this area are tolerated, the out of gamut color will be replaced
with a color recipe that does not have the same L
value.
On the other hand, when entering the value 100,
the program will make sure that the replacing color mixture has the same L value.
Color Purity
The Color Purity tab lets you define how the colors that are far off the gamut should be
cleaned up. In this case, cleaning colors means that if e.g. you print a saturated cyan that is
out of gamut and can only be printed as a combination of cyan and magenta, the cyan value
will be corrected far upwards while the magenta values will be corrected downwards.
RGB Special
In the RGB-Special tab you can set a special handling for certain colors to prevent them from
drifting off too far. Namely this concerns shifts from blue to violet, red to orange and green
to yellow, which can be prevented or allowed in this dialog.
Creating Printer Profiles with ColorGPS
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Color Gradients
The Color Gradients tab is used to prevent so called “Graying” in gradients from dark saturated colors to black. As a bonus, other color gradients are automatically smoothed as well.
However, with a low total ink limit (below 300%), setting a high value can also result in the
contrary than what you hope to achieve.
ColorBoost Option
The Color Intensity (Color Boost) option allows increasing or lowering the intensity of the
measured values without having to print a calibration chart with this changed color intensity.
For example, this could be used to compensate for measuring a
transparent medium with a spectrophotometer that can only
perform reflectance measurement and thus, returns measurement values that are not bright enough.
Drag the slider to the right (higher value) to increase the color
saturation. After having changed this value, you do not have to
reprint and re-measure the calibration; you just have to recalculate the profile.
Since the color intensity value is only saved in the profile data we strongly recommend to
mention the value in the profile description so that you will be able to easily recognize these
special profiles some time later.
Please note that in most cases this feature will adversely affect the color accuracy.
Creating Printer Profiles with ColorGPS
12
Choosing the Correct GCR
The following GCRs are available to create an ICC grid.
This GCR uses no black inks, meaning that all
gray tones on the axis from black to white
are mixed from CMY.
100%
100%
75%
50%
25%
75%
used ink
No Black (GRC0)
50%
25%
black value 0-100%
Using GCR1, the black and gray tones in
light areas are printed with only CMY. Black
ink is only used starting at 50% of the black
value.
100%
100%
75%
50%
25%
75%
used ink
Black only in Shadows (GCR1)
50%
25%
black value 0-100%
GCR 2 is similar to GCR1, whereas black (K)
can be used sooner, which leads to less
CMYK being applied.
100%
100%
75%
50%
25%
75%
used ink
Black in Dark Tones (GCR2)
50%
25%
black value 0-100%
Creating Printer Profiles with ColorGPS
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The middle GCR is a more extreme variant of
GCR1 + 2. With this GCR, black inks can already be used in middle tones.
100%
100%
75%
50%
25%
75%
used ink
Black from middle Tones (GCR3)
50%
25%
black value 0-100%
GCR4 allows to print with maximal linear
rising black from the beginning. At the end
of the curve CMY is used to create a deep
black.
100%
100%
75%
50%
25%
75%
used ink
Black also in Light Tones (GCR4)
50%
25%
black value 0-100%
User defined Black (GCR+)
GCR+ provides the possibility to define a custom black
buildup, respectively setting up on your own how the
black ink should be used.
Using the slider that can be moved between the values 0
and 100 the user can set from which brightness value between paper white (0) and maximum black (100) the black
ink should be used.
Creating Printer Profiles with ColorGPS
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