After you’ve created the Density Linearization and determined the Total Ink Limit, it’s finally time to move to the Color Profile, the final step in the color calibration of your printer.
The Color Profile examines how different color mixtures look printed out and, therefore, how they have to be adjusted to achieve specific looks and colors. To do this, a chart with color patches made up of mixed colors is printed and then measured using a spectrophotometer. Ergosoft's color profiler, ColorGPS, also features many customization and tweaking options that let you customize the output in different ways, such as increased saturation, etc. Additionally, it has direct access to the density and ink limit data, which allows for more accurate profiling data than other standalone profilers can provide.
ColorGPS can also be used to create RGB profiles for printers that support RGB Ink setups. To do so, simply select a Print Environment using an RGB color setup before beginning the calibration process. ColorGPS will automatically switch to RGB mode, and you can follow the instructions below as normal.
The resulting ICC profile is then saved and embedded in the Print Environment.
To begin with the color profiling process, you’ll need:
A Color Measuring Device (Spectrophotometer).
A Print Environment set up to connect to your printer with a port and PrintQueue.
The material and inks you want to calibrate are loaded into your printer.
A finished Density Linearization and Ink Limit made with that same material and inks for your Print Environment.
To use the spectrophotometer, we’ll first need to detect it in the software. Go to Tools > Application Defaults > Application > Spectrophotometer. From the Spectrophotometer dropdown menu at the top of the dialog, select the measuring device you are using and click the Detect button. The RIP will establish a connection to your measuring device. If the connection is successful, it will display the type and serial number of your device. The other settings in the Spectrophotometer dialog can be left to default in most cases unless you specifically want to use a different measurement standard or if you are using a special application such as white underprinting, primer, etc. In that case, adjust the settings as required. Confirm with Ok to exit the Application Defaults window.
Note that while working with ColorGPS Wizard, you can save your session at any time. Should you need to interrupt your work, simply go to File > Save or File > Save as... to save your ColorGPS session as a *.cpd file. Whenever you want to pick up again, simply start ColorGPS again and go to File > Open... and select the *.cpd file of the session. This is also an easy way to quickly iterate between different variants of a profile, as you can load a cpd, change some settings, and regenerate the profile directly (Some changes may require you to measure a new chart, though).
The exception here is in-progress measurements, as they are not saved until completed. If you need to quit during a measurement, you can save it separately in the measure dialog, though.
Start ColorGPS either through the Icon in the Toolbar or by going to Tools > Linearization & Profiling Tools > ColorGPS.
The first window you’ll see shows a summary of the data that the profile will be based on. The dropdown menu at the top lets you select the Print Environment that will be used for the printer port and print parameters such as resolution, passes, etc., to print the calibration chart. The profile we create will be embedded into this Print Environment. By default, this will be the Print Environment currently active in the JobComposer.
Below the dropdown, you’ll see the description for that Print Environment and the density file that will be used as the basis for the color profile, along with its description.
At this point, you can verify if all selections are correct and then click Next to proceed.
This is where we’ll configure and print the color chart for the profile. There's a bunch of settings to configure before printing the chart, luckily they are arranged so we can just go through them top to bottom!
For clarity, we will focus on the main options in a straightforward profiling process. For information on the more in-depth settings found in ColorGPS > Options, check the Advanced Options section further down.
Total Ink Limit: This setting is technically the same as the one in the Print Environment that we determined in the Total Ink Limit article. In most cases, this should be the same as the value determined there. It is possible to enter a different value here, but that should be used with caution as it can lead to color inaccuracies, especially when using lower values in the profile than in the Print Environment.
Black Generation: Determines the use of black inks while printing mixed colors. Different GCRs have different points where they start using black ink to darken color tones in mixed colors. For example, Black in Dark Tones (GCR 2) will not use black until colors get very dark, while Black from Middle Tones will start printing black to enhance colors much earlier in colors of mid-lightness.
Using Black in earlier and in lighter tones increases the range of printable colors and saves ink, but depending on your inks, printer, and material, the dark dots can be visible in the lighter tones and make for «dirty» looking printouts.
ColorGPS will preselect a recommended setting for you based on the colors set in the Print Environments. Of course, you can always select a different one based on your preferences.
No Black (GCR 0) will not use black ink at any point; rather, dark areas will be printed by mixing other colors together (e.g., CMY)
Black Only in Shadows (GCR 1) prints black and gray tones in light areas using only CMY, black ink starts being used at around 50% black value.
Black in Dark Tones (GCR 2) is similar to GCR1 but uses black sooner, so less CMY is used.
Black from Middle Tones (GCR 3) allows for black inks to be used in middle tones to enhance colors, again reducing the use of CMY.
Black in Light Tones (GCR 4) uses black throughout the lightness range in a linear fashion. The darkest black areas, however, are made up of CMY to create the deepest possible black.
User-defined GCR (GCR+) lets you create a custom GCR to control the use of black ink. Click Adjust to set the black behavior as desired by moving the slider back and forth to control the earliest point where black ink may come into play.
Ink Mixing Model/Scattering Factor: allows for the factor in an additional light scattering parameter. To predict the resulting color when mixing inks, this feature uses advanced optical modeling based on light scattering theory.
By considering light scattering in spectral color measurements on inhomogeneous materials (textured or matte materials), a more accurate color simulation can be achieved. This is especially powerful in combination with the so-called ColorGPS QuickColor profiling.
The light scattering can either be set manually using the slider at the bottom of the dialog, or the optimal value can be estimated based on the measurement values from the density linearization.
Estimating the values requires that you activate the option “Print mixed patches for scattering prediction” for your density linearization and measure the mixed patches in the density chart.
Precision of Calibration Chart: Determines how accurate you want your profile to be. Setting a higher number will lead to a larger number of patches to be printed and measured, and the higher you go, the smaller and more incremental the improvements between different precision settings will be.
Once you’ve made the settings, click Calculate Calibration Chart to create a Calibration Chart with your settings. The No. Of Patches field below will then show you how many patches the chart contains. You can use the Size of Calibration Chart to adjust the number of patches if, e.g., you want to make sure the chart fits on a certain number of pages. Keep in mind not to reduce the number of patches too much, though, as a lower number of patches means a lower precision in the profile.
Once we have calculated and adjusted our calibration chart, we’re ready to print and measure it. Press the Print button to send the Job to the printer.
Test Chart Size: Use this to have the RIP calculate if a chart with your settings would fit the material, how many pages it would require, etc.
Print: send the Calibration Chart to the printer. The chart behaves like any other in that it will go straight to the PrintQueue and wait to be sent out from there. If it isn’t already, set your PrintQueue to Online to send the Job on its way.
Measure: Brings up the Manage Measurements dialog to start the measuring process after the chart has been printed. Before the chart has been printed, the button is unavailable.
Show Measurement: Displays the measurement results of the last conducted measurement in this ColorGPS session.
Generate Profile: After measuring, this button will finish the profiling process and generate and embed a color profile. But we're not quite there yet, first we’ll need to measure the chart.
After configuring the parameters for our color chart and printing it, we’ll need to measure it. Ready your Spectrophotometer and get the printed chart handy.
Click the Measure button in the ColorGPS window to reach the Manage Measurements dialog.
On the top left, you’ll see your Color Chart Pages list. If your chart is broken up into multiple pages, you’ll see all of them here. This is also where you select which chart you want to measure, so make sure to select the first one before beginning your measurement.
On the bottom left, you’ll see the Measurements section, which lists all the measurements you conducted for this page in this session so far. At first, you’ll only see the expected listing as there are no actual measurements yet. When you have more measurements, you can toggle them to be visible or not visible in the preview in the center of the dialog.
In the center, you’ll see the Color Patches. Initially, they will only show the expected values for each color patch. But as you conduct Measurements, they will be added to the view so you can compare the measured values with the expected ones and quickly spot outliers and measurement errors.
At the top right, you’ll see the section dedicated to showing information about the currently selected patch. When you have measurements available, it will show what values were measured and how your measurements compare to the expected values by numbers.
The Spectrophotometer button brings up the measuring device detection again. This way, you can swap measuring devices when needed, redetect it if the connection is lost, or just detect your Spectro if you missed connecting to it in Application Defaults > Tools.
Click Measure... to begin measuring, since we have already detected the spectrophotometer, it should automatically be recognised and ready (Though it might ask for a white calibration).
The Next Measurement Section shows you which line is to be measured next. You can switch between Single Measurement (Measure every patch individually) or Scan measurement using the buttons to the right.
The Measurement Values section shows you the last measured line and both the measured values (Top) and the expected values (Bottom). On the bottom right, you’ll also see the DeltaE difference between the measured and expected values for the currently selected pair.
Once you have measured all the lines, you can click Ok to save the measurements and go back to the Manage Measurements dialog. From here, we strongly recommend starting another measurement for the same chart page. Repeat this for every chart page you have until you have at least two measurement passes for each page. This allows the RIP to create an average between the different measurements and eliminate accidental discrepancies and measurement errors.
Note that ColorGPS will create an automatic backup of your measurement results every time you exit the measurement dialog. Should you need to reload a previous session's measurement results for any reason, you can find these backed-up measuring sessions in [UserDataFolder]\Data\Color\Measurements\AutoSave with the naming convention [ColorChartId]_[NameOfPrintEnvironment]_[timestamp].cxf.
When you are finished, click Ok in the Manage Measurements dialog to have the RIP calculate the average between all the measurements and take your measurement results back to the ColorGPS window.
We’re already at the finish line. After you’ve measured all the pages of the chart and returned to the ColorGPS window, click the Generate Profile button to have the RIP use the measurement values to create your color profile for you. This process can take several minutes and will show a process bar for the duration. Make sure not to close the RIP or shut down your PC during this time.
Once the calculation is finished, the profile is automatically embedded into the Print Environment you selected in the first ColorGPS window. If you are in Print Environment > Quality, you’ll see that the Profile segment now shows Embedded.
That’s it, you’ve made it! Your calibration is now ready and will automatically be applied every time you print an image with this Print Environment. At this point, we’d recommend doing one or two test prints to check how the profile came out. If you are satisfied, you’re ready to start the first of many production runs with your new profile!
While the regular color calibration process is fairly straightforward, ColorGPS offers a lot of in-depth, advanced options that allow you to influence the color profile. From increasing color intensity to altering the hue of blacks in your pictures, there are many ways to customize the output results your profile generates. Please note that these features are intended for advanced users, however, and require technical knowledge in ColorManagement to be used effectively.
If you save your ColorGPS session after measuring the color chart (ColorGPS > File > Save...), you can load it again later and make further adjustments to these settings.
Simply load the saved .cpd file (ColorGPS > File > Load...), adjust the color options to your liking, then generate the profile again. You don't even need to conduct a new measurement.
Found in Options > Calibration chart, and contains settings that concern the layout of the color calibration chart.
Geometry lets you select the chart geometry that is used when generating the color chart. This should match the spectrophotometer you intend to use for measuring. If you have detected a Spectro in Tools > Options, ColorGPS will autoselect a suitable geometry for it.
The number of Patches per row defines how many color patches can be on a single row in the chart. When making changes here, keep in mind that most measuring devices have a limit to how many patches per row they can measure.
Using a fixed chart layout will lock the calibration chart quality to 100% and will not remove similar or equal patches from the chart dynamically, as the regular chart generation feature does. This can dramatically increase the number of patches to be read, but can be useful if you find your charts turning out with few patches due to a limited amount of ink in the printer.
Edit Job before Printing enables you to edit your color chart before it is printed. When this option is active, clicking Print in ColorGPS will load the chart into the JobComposer instead of sending it to the printer. You can then save your session, close ColorGPS, and make changes to the chart in the JobComposer. Note that some changes, such as scaling, can cause the chart to not be read properly anymore.
To avoid wasting material on misprints of individual patches or areas of the chart, you can use Print multiple Charts across Job Width and Print additional Charts rotated 90 degrees across Job Width. This prints the same chart across your material multiple times to increase the chances that each color patch is properly printed at least once, so it can be measured if you have a difficult printer on your hands.
Use multiple columns to print a chart to save media, divide the chart into multiple parts/columns that can be spread across the media width.
Let you set how the black reference for the profile should be mixed.
Blackest Black focuses on reaching the darkest possible black by using lots of color inks. This makes for dark blacks, but can lead to visible color tints in dark black areas.
Darkest Neutral focuses on keeping black tones neutral. It will likely not achieve the same deep blacks as Blackest Black, but it avoids color tints in dark areas.
You can also select between two custom Scaling of Brightness modes available for the Black Point. These only affect the Perceptual and Saturation Rendering Intents.
Linear Y scales are similar to black point compensation.
Linear L scales the same way as the standard scaling used in V14 of ColorGPS.
Limits the use of additional profile colors (E.g., OB in CMYKOB) in light color tones to avoid visible color dots in those areas. To limit a color, select it from the dropdown menu and uncheck Auto. You can now see where the color starts being used by entering an L value on a scale from 0-100. The higher the value, the earlier additional colors may start being used. Colors outside the limit will be mixed strictly using CMYK, even if the profile would normally use an additional color.
Affects the accuracy of the profile by setting the number of grid points for the gamut calculation. A higher amount of grid points leads to a more precise profile, but will require a longer time to calculate and cause the *.icc file to become larger.
The following features in ColorGPS > Options are part of the Profile Editor set
Controls which areas of the profile should allow for high contrast, i.e., textures. Contrast is controlled through saturation, where saturated and unsaturated colors (Dark and light tones, respectively) may have more or less saturation.
Both the Perceptual and Saturation Rendering Intents will have the brightness contrast for their maximum black adapted automatically, so the neutral setting of 100% usually delivers the best results.
Decreasing the contrast causes the colors on the outer edges of the gamut to gain textures as well, increasing the apparent gamut.
Controls how out-of-gamut colors are calculated. This does not effectively enlarge the gamut but rather gives you tools to indicate to the RIP and profile how you want to deal with colors that can not be printed with the printer's color space.
Auto Preserve Hue automatically maps the gamut in a way that preserves the hue of out-of-gamut colors.
Gamut Mapping 14 reverts the gamut mapping to the way it was in version 14. For a detailed description, see the V14 Application Note Creating Printer Profiles with ColorGPS.
Color Purity deals with colors that are far outside the gamut of the profile, depending on the rendering intent. A higher setting for Color Purity means that for out-of-gamut colors, the rendering intent will increase the amount of the strongest color in the color mixture. E.g., imagine an out-of-gamut Cyan tone made up of Cyan and Magenta. A high color purity will mean that since the Cyan is dominant in the color mixture, it will be increased, while the Magenta is decreased to get a higher purity of Cyan.
Color Gradients is used to prevent so-called Graying effects in gradients going from dark saturated colors to black, but also has a smoothing effect on all other types of gradients. However, it’s important to note that when using a low Total Ink Limit (Below 300%), using this function may lead to the opposite effect and actually decrease smoothness in gradients.
Deals with transitions between areas with different color recipes. Generally, ColorGPS will attempt to use ink mixtures that are as close to the target LAB as possible. In some cases, this can lead to sudden changes in ink composition that can look like banding in gradients.
To counteract this, ICC Profile smoothing influences the transition areas between ink recipes. The dialog lets you control the smoothing level (How much smoothing is applied) and the number of repetitions for the smoothing procedure.
Note that gradient smoothing can lead to visible changes in other color tones.
After you’ve measured a color chart, ICC Color Intensity lets you lower or increase the intensity of colors in a profile without having to conduct a second measurement.
Dragging the slider to the right (Higher value) will increase color saturation, to the left will lower the saturation. Assuming you’ve already printed and measured a chart, you don’t need to repeat the process after changing this setting, as it directly affects the already measured values. You can simply change the ICC Color Intensity setting, confirm, and then press Generate to recalculate the profile with the new intensity values.
This can be used to generally increase or decrease saturation in your profiles, but can also help when, e.g., measuring a transparent material and your returned measurements aren’t bright enough.
Note that using this feature can negatively affect color accuracy.