why different colors

Forum|Forum|4 years ago
September 2, 2021
2 replies
327 views

Hello everyone, please tell me why here on the rectangles the layer shows different colors.

psh.zip

Windows

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Correct answer davescm

Your two squares are not the same colour.

The yellow channel in the right hand square is at 100%. The yellow in the left 99% .

The maths for blending each channel in colour dodge is Background/(1-Foreground). In the case of CMYK the layer values are inverted before the maths and the result inverted after.

It all works smoothly until the foreground layer is 0% which inverted is 1 and the background is 100% which inverted inverted is 0. That results in maths which is 0/(1-1) = 0/0 which gives an error for which 0 is used and is then inverted to become 100%. i.e. the channel remains at 100%

Dave

davescm

Correct answer

Community Expert

Your two squares are not the same colour.

The yellow channel in the right hand square is at 100%. The yellow in the left 99% .

The maths for blending each channel in colour dodge is Background/(1-Foreground). In the case of CMYK the layer values are inverted before the maths and the result inverted after.

It all works smoothly until the foreground layer is 0% which inverted is 1 and the background is 100% which inverted inverted is 0. That results in maths which is 0/(1-1) = 0/0 which gives an error for which 0 is used and is then inverted to become 100%. i.e. the channel remains at 100%

Dave