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How Colours are Selected in Selective Colour (and How to Use This in Practice)

Disciplines > Photography > Affinity Photo > The InAffinity Video Index > How Colours are Selected in Selective Colour (and How to Use This in Practice)

Summary | Video | Detail | See also

Summary

The Selective Colour adjustment is one of a number of controls which first makes a pixel selection and then applies an adjustment to these. Exactly how colours are selected is explained carefully, with a numbers annotations (do pause the video to read these as needed). With this knowledge, you then just need to look at the RGB values of any pixel or area and will immediately know which colour selection, from Red to Magenta, to choose.

Video

Click image to watch on YouTube:

Detail

Publication Date: 16-May-22

Duration: 6:06

In summary:

Selection

• Red selects pixels where R has the greatest value
• Green selects pixels where G has the greatest value
• Blue selects pixels where B has the greatest value
• Yellow is selected when B has the lowest value
• Cyan is selected when R has the lowest value
• Magenta is selected when G has the lowest value

Adjustment

• Red adjustments have greatest effect when R is much higher than the next highest channel value
• Red adjustments have little effect when R is close to the next highest channel value
• Green adjustments have greatest effect when G is much higher than the next highest channel value
• Green adjustments have little effect when G is close to the next highest channel value
• Blue adjustments have greatest effect when B is much higher than the next highest channel value
• Blue adjustments have little effect when B is close to the next highest channel value
• Yellow adjustments have greatest effect when B is much lower than the next lowest channel value
• Yellow adjustments will have little effect when B is close to the next lowest channel value
• Cyan adjustments have greatest effect when R is much lower than the next lowest channel value
• Cyan adjustments will have little effect when R is close to the next lowest channel value
• Magenta adjustments have greatest effect when G is much lower than the next lowest channel value
• Magenta adjustments will have little effect when G is close to the next lowest channel value

Hence:

• All pixels can be changed by one primary (RGB) and one secondary (CMY) Colour selection as there is always a maximum and minimum value (but watch out when two or more channels have the same value).
•  The middle channel value controls the strength of adjustment values between the primary and secondary Colour selection.

For example if R is highest and B is lowest, both Reds and Yellows Colour selection can be used. The value of G will determine the strength of the effect when using sliders under Reds and Yellows. A lower G value will make Reds sliders more powerful and Yellows sliders less effective. A higher G values will make Reds sliders less powerful and Yellows sliders more effective.

Adjusting monochromes (Whites, Neutrals and Blacks), where R, G and B have similar or close values, is covered in another video.

See also

Affinity Photo Tutorials on Selective Colour

Affinity Photo Tutorials on RGB

Affinity Photo Tutorials on CMYK