Before you either paint from a photo on the computer or measure a color sample, you need to calibrate the brightness of the computer screen. You overlap a white card (lit by a light source) with the white patch of this screen. Then adjust the brightness the screen until the screen brightness matches the card brightness. Then you can load your reference photo on this computer for painting, or measure your color sample.

Computer screen brightness adjustment tool

Qiang Huang  

  

Painter's Guide
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Settings

Color wheel size:

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100
50
0
-50
-100
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10
9
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6
5
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3
2
1
0
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