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dmstraker

Contrast Negate blend mode (still trying to figure it out)

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I'm trying to figure out what exactly is happening in the Contrast Negate blend mode.

It seems there are two 'opposite' groups: RBM and GYC, so Red is opposite to Green, Blue opposite to Yellow and Magenta opposite to Cyan. Then you get effects such as when both layers are the same, you get the opposite colour, but if the layers are opposites, you get the bottom layer colour (otherwise the top layer).

The best use so far I've found for it is when overlaying an image with text, so the text is always contrastive.

Am I heading in the right direction? Any suggestions?


Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

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It does not mention the Contrast Negate blend mode specifically, but this "Photoshop Blend Modes Explained" article has some useful info in its Contrast Group section that may give us a clue or two about how it works. From that section:

Quote

All of the Contrast modes work by lightening the lightest pixels, darkening the darkest pixels, and dropping the gray mid-tones (50% gray). {...} For each of the Contrast blend modes, the math is applied against complementary (opposite) blend modes.

The article explains what complementary blend modes are & the "standard" (more like "normalized" to a mathematician) math that PS uses.


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5 hours ago, R C-R said:

It does not mention the Contrast Negate blend mode specifically, but this "Photoshop Blend Modes Explained" article has some useful info in its Contrast Group section that may give us a clue or two about how it works. From that section:

The article explains what complementary blend modes are & the "standard" (more like "normalized" to a mathematician) math that PS uses.


Useful note. Thanks, RC-R. The Overlay etc. group indeed act this way and perhaps Contrast Negate is some kind of inversion of these. As an experiment I overlaid an image with a 50% grey layer and set Contrast Negate blend mode. All that is visible is 50% grey. Which is a kind of opposite, I guess to Overlay. I tried painting with white and black. Both, interestingly, gave the same result, which was a pretty extreme black/white solarization.

Painting with other colours in the blend layer also gives a solarization, but now with these colours and their inverse as the two solarized colours. Blending a duplicate layer with Contrast Negate gives an odd recolour effect. Interestingly, Negation has a similar, and more colourful effect. Negation uses the formula 'Int(Base + Blend)'. Maybe Contrast Negate uses some variation on this.


Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

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Here's an interesting discovery:

1. Duplicate image. Blend Mode: Contrast Negate. Note how image looks.

2. From the beginning again, add Pixel layer above image. Fill with white. Blend Mode: Negation. Aha! It looks the same as 1.

So they are related. TIme to sleep on it, perchance.


Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

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