Spreadsheets to Estimate Dot Gain from Lab Measurements

Occasionally someone wants to know the dot gain of a CMYK output device, but they lack the density measurements needed by the Murray-Davies equation. All they have is Lab measurements. I have prepared two Excel spreadsheets that estimate the dot gain from the Lab measurements of sets of CMYK colors. They are available here as downloads:

File Name File Size Description
LabDotGainCalculator1.sit 17K Nine patches. Calculates dot gain at 50% points only.
LabDotGainCalculator1.zip 13K Nine patches. Calculates dot gain at 50% points only.
LabDotGainCalculator2.sit 66K 84 patches. Calculates dot gain at 0%, 5%, 10%, …, 95%, 100%. Includes graphs.
LabDotGainCalculator2.zip 60K 84 patches. Calculates dot gain at 0%, 5%, 10%, …, 95%, 100%. Includes graphs.

The method I use is documented here.

If you are working from a CMYK ICC device profile, you can obtain the necessary Lab values from the profile using Photoshop.

  1. Open Photoshop's Edit/Color Settings window (Advanced Mode).
  2. Select your profile as the CMYK Working Space.
  3. Select Absolute Colorimetric for the Intent in the Conversion Options.
  4. Close the Color Settings dialog.
  5. Open the file "LabDotGainCalculator1.tif" or "LabDotGainCalculator2.tif" (included in the downloads) and assign the Working CMYK Color Space.
  6. In the Info window (Palette Options) set the Second Color Readout to Lab.
  7. Position the eye dropper tool over each of the color patches and record the Lab values for each.
  8. In the spreadsheet "LabDotGainCalculator1.xls" or "LabDotGainCalculator2.xls" enter the Lab values recorded above.
  9. The dot gain values are displayed in the spreadsheet.
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