dmstraker Posted July 23, 2017 Share Posted July 23, 2017 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? Quote 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. Link to comment Share on other sites More sharing options...
toltec Posted July 23, 2017 Share Posted July 23, 2017 My only suggestion is to let me know when you do figure it out. It's a weird one, Quote Windows PCs. Photo and Designer, latest non-beta versions. Link to comment Share on other sites More sharing options...
R C-R Posted July 23, 2017 Share Posted July 23, 2017 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. Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
dmstraker Posted July 23, 2017 Author Share Posted July 23, 2017 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. Quote 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. Link to comment Share on other sites More sharing options...
dmstraker Posted July 23, 2017 Author Share Posted July 23, 2017 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. Quote 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. Link to comment Share on other sites More sharing options...
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