Press Recalibration

Varying conditions such as temperature and humidity can cause undesired printer deviations. To ensure that your printing results fall within the print standard's tolerances despite these environmental factors, we recommend regularly recalibrating your digital press.

The structure of the recalibration dialog

You can access the recalibration dialog from both Resources > SmartProfiler and Hotfolder > PDF-Hotfolder by selecting a printer-media combination and clicking the Recalibrate button in the toolbar.

This image shows the recalibration dialog.

1. Calibration Info: The information panel on the left displays the name and comment of the corresponding GMG SmartProfiler document or hotfolder, depending on where you opened the recalibration dialog. Both fields are read-only in the recalibration dialog and can only be modified in the respective document or hotfolder.
    
2. Last Results: Here the results of the last completed calibration are displayed, if one has already taken place. If the last calibration was only done for a subset of inks, the deactivated channels are displayed in gray. Please note that the results of the ongoing recalibration are listed under Current Calibration.
    
3. Quality Criteria: To achieve a successful printer calibration, the measurement results during recalibration must fall within the Delta E thresholds defined here, which may take several iterations. While you can opt for higher thresholds to reduce the number of iterations and speed up the process, be aware that this may come at the cost of color accuracy.
    
4. Current Calibration: Here you can see and adjust the ink configuration and start the recalibration process. You can also import () and export () measurement data. The Delta E results of the current calibration will be listed below the toolbar, and if you want to inspect the calibration data in detail, you can show the printer color space () in GMG GamutViewer (see "Inspect and optimize recalibration results").
    

Recalibrate the press

You can either recalibrate the full ink set of your digital press or just a subset of inks to save costs and reduce calibration time. Recalibration involves printing and measuring test charts, evaluating the results, and updating the printer calibration file. Multiple iterations may be needed to achieve successful recalibration, ensuring that the target values meet the defined quality criteria.

How to recalibrate your digital press:
 

1. Under Resources > SmartProfiler, select the printer-media combination that you want to recalibrate.
   
2. Click on Recalibrate to open the recalibration dialog.
    
3. Under Current Calibration, adjust the ink configuration according to your needs.
   If you do not want to recalibrate all channels but only a subset of inks, you can activate and deactivate channels by clicking on the matching color patches. Deactivated channels will be displayed crossed-out.
   
4. Click the Recalibrate button to start the recalibration.
   The Measurement: Calibration dialog opens.
    
5. Print and measure the recalibration test chart (see "Printing and Measuring Test Charts").
    
6. After you have finished the measurement, go back to the recalibration dialog.
   
7. Evaluate the calibration results listed under Current Recalibration.
   If the quality criteria have not been reached during this iteration, this will be indicated by a red status light. In this case, click the Recalibrate button again to start another iteration with an adjusted test chart. You can repeat this step until the results meet the defined quality criteria (see "Inspect and optimize recalibration results").
   
8. If the quality criteria are met, this will be indicated by a green status light. In this case, click the Publish button to accept the results and complete the recalibration process.
   
   The profile under Resources > MX profiles will then be updated, and that update carries through to the hotfolder using this printer calibration.
   Details on the last calibration will also be displayed in the overview under both Resources > SmartProfiler and Hotfolder > PDF-Hotfolder when the printer-media combination is selected.

Inspect and optimize recalibration results

The results of the ongoing recalibration are listed under Current Calibration. Each iteration of printing and measuring is shown as a row in a table. A status lamp indicates whether or not the Quality Criteria have been fulfilled: A red light indicates that the quality criteria are met, a green light indicates that they are not.

In this example, the defined tolerances are met after three iterations.

Clicking the magnifier icon () next to an iteration brings up a table with all measured and target values for all patches. This can help identify the issue if the printer cannot be calibrated. For instance, if the highest Delta E values appear correlated to a specific color channel (sort columns by delta E and view input ink builds), you may need to replace the ink or clean the print heads. If the paper tint values (0, 0, 0, 0) are out of tolerance, it could indicate that the wrong media type was loaded into the printer.

You can also click the spider web icon () in the toolbar to inspect your calibration data and show the printer color space in GMG GamutViewer.