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I'm struggling to get the same result in the Blender node editor when layering images with transparency, to the result I get when doing the same in Photoshop.

The Blender result is shinier/washed out compared to the result from Photoshop (see below).

The blend file can be found here: https://drive.google.com/file/d/0B54MopLgZnccM2VnVWVTLUxlNUk/view?usp=sharing

I've played around with Premultiplied and Straight Alpha, tried 32 bit pngs, mix nodes and Alpha Over nodes, and pulling out my hair, but haven't been able to find the answer.

Comparison

Thanks for any help!

Mark.

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Muck Muddy
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    related: http://blender.stackexchange.com/questions/28284/colour-shift-when-viewing-render-outside-of-blender/29006#29006 –  Mar 01 '16 at 01:42
  • Thanks @cegaton for the link. I'm not sure if it's colour/monitor issue, as the Blender result looks the same in both Blender and Photoshop, as does the Photoshop result. I've also tried saving the overlay with and without the ICC profile, but this didn't fix the issue either. I will keep investigating the colour profile anyway... – Muck Muddy Mar 01 '16 at 02:28

2 Answers2

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Photoshop has a non-linear reference space typically, and as such, all blends are wrong.

Blender's compositor on the other hand, uses a strictly linearized reference space, and alpha overs, assuming you are using associated alpha and the Alpha over node, are correct.

Nonlinear Over: Nonlinear Over

Linearized Over: Linearized Over

troy_s
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  • Thanks Troy. That seems like a good answer, though not one I was hoping for. :-) Do you know if there's a way to ask Blender to not be so strict on the linears? – Muck Muddy Mar 01 '16 at 22:23
  • No. You actually always want this. See https://docs.google.com/presentation/d/1-6sF9XjjZclJ43NDi4fAelVybeCZpp7mOiA2wpxlitA/edit?usp=docslist_api if you don't understand why. Photoshop has a hack "linear blend" mode. Fundamentally, you always want linearized blends. If you absolutely want broken backwards blending, use an alpha over in the VSE. Awful idea however. – troy_s Mar 02 '16 at 04:50
  • Do different colour profiles effect how the alpha is treated? Because all of the colour in the image that is fully opaque is identical in Photoshop and Blender. I would have thought that if it was a colour profile issue, all of the colours would be different, not just the alpha. But I don't know much about colour profiles. – Muck Muddy Mar 02 '16 at 04:52
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    It isn't a colour profile issue if the two colour spaces are identical. It has to do with how light mixes, which is a linear radiometric effect. Photoshop and other anachronistic image editing tools are nonlinear, display referred models. This means the blends are nonlinear and, as a result, wrong. Try a fully saturated red star, slightly blurred, over a cyan (blue and green) background. See how broken it is? – troy_s Mar 02 '16 at 08:25
  • A-ha! Thanks for sharing your brains, some really great learnings. I've found if I work in 32 bit mode in Photoshop, I get the same effect as in Blender. Is that the only way to set the light mixes to linear in Photoshop? Thanks! – Muck Muddy Mar 03 '16 at 22:57
  • Yes, but remember in Photoshop that is a hack, and will only pseudo-linearize the operation for sRGB imagery, and only for that operation. It is an anachronistic behemoth with legacy code. It will likely remain that way for a long, long, long broken time. – troy_s Mar 03 '16 at 23:05
  • Ha ha. Poor Photoshop. I also found that, going to Edit > Colour Settings > Blend RGB Colours Using Gamma (1.00) makes the overlay look the same as in Blender too. – Muck Muddy Mar 03 '16 at 23:44
  • You can use a linearized ICC profile as a working space if you are interested. It would require working at at least 16 bits per pixel. – troy_s Mar 04 '16 at 21:58
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I opened the file, and immediately it looked like the photoshop reference you posted (No mods to your file), see attached.

enter image description here

Rick Riggs
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