Background

You can create a print calibration curve to adjust tonality by simultaneously calibrating cyan, magenta, and yellow inks so that neutral shades of gray are maintained, while black is calibrated separately for lightness and darkness.

Tasks

Goal
Create a print calibration curve to an industry standard for gray balance using a P2P51 chart.  (A simple Tint Ramp chart is not suitable, as you must use a measurement chart that contains required gray scale patches in order to be able to measure and compute gray balance.)

Task 1: Create the print calibration curve

  1. In ColorFlow, click the Print Curves tab.
  2. In the Calibration Curves section at the top left, click the Add button .
    The Devices dialog box appears.
  3. Drag the device "XX Offset Press" that you created in a previous activity to the viewer window and close the Devices dialog.
  4. Click the Properties icon  in the Offset Press panel and define the device condition:
    1. From the Plate Setup list, select None. You can also select a plate setup defined in the Plate Curves tab.
    2. From the Screening list, select  20u Staccato  or add the value to the list if it doesn't exist. Skip this step if you selected a plate setup above.
    3. From the Substrate list, choose Type 1 or 2 (coated art) 170 g/m2.
    4. Leave Process Inks as CMYK
    5. Click OK.
  5. Click the Measurement icon . (Note: Measurement icon will appear as  if you have already created an offset press with the same properties in a previous exercise.)
  6. In the Charts panel, use the Measurable by list control to select your measurement device.
  7. In the Charts list, choose a P2P51 chart suitable for your measurement device.
  8. In a real-life situation, you would Export the P2P51 chart, output the chart from Prinergy, print the chart on press and measure it in ColorFlow.  For the purpose of this training, you will import a sample P2P51 measurement data file:
    1. Click the Measurements tab.
    2. Click Import.
    3. Leave the Characterization
    4. In the Characterization Print Curve dialog, leave the Print Curve as the default Linear (None) and click OK.
    5. Select the sample P2P51 sample data file. 
    6. Click OK. (If you have used an existing Offset Press device condition, you will get a message saying Device Condition Response Update: This action will update curves and profiles in color setups using the device condition, discarding adjustments. Continue? Click Yes.)
    7. Click Close.
  9. Define the calibration target to an industry specification:
    1. Click the Calibration icon  in the link area between the Calibration Target and the Offset Press panels.
    2. Ensure the Show curves in Prinergy check box is selected in the Conversion Definition dialog.
    3. In the Process Inks tab, choose GRACoL 2006 Coated 1 from the Target list.
    4. Curves Method: Gray Balance is selected automatically.
    5. Leave the 3/4-tone Correction with the default value.
    6. Click OK.
      A print calibration curve is generated to match the gray balance specification for the chosen industry specification. 
  10. In the Calibration Curves table list in the top left, double-click the name of the curve you just created and enter XX new print calibration curve for gray balance (where xx= your initials). Hit the Enter or Return key to set the name.

Task 2: Output a page using the print calibration curve in Prinergy

  1. In Prinergy, create a new job, and name it as XX print Curve for gray balance (where XX = your initials).
  2. Refine GrayBalanceTestFile.pdf with 1stRef-Normz.
  3. Output the PDF file using Virtual Proof.LoosePage with the print curve you just created:
    1. In the Virtual Proof.LoosePage Process template dialog box, from the Output To list, choose Virtual Proof.
    2. Leave ColorFlow Color Relationship Management unchecked.
    3. Expand the Calibration & Screening panel.
    4. Click the ColorFlow Current State radio button.
    5. Expand the Print Curve drop down list and select XX new print calibration curve for gray balance.
  4. Open the generated output in VPS and measure the 50% patch. 
    Confirm that the gray balance print calibration curve has been applied: 50% cyan should measure 51.4. 50% magenta should measure 53.5. 50% yellow should measure 52.2. 50% black should measure 44.1. (Your measurements may vary by .1-.2%)

Outcome

You have created and applied a print calibration curve to match output to the GRACoL 2006 gray balance specification.

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