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I have an image of some fire with an alpha background.

[IMAGE]

When rendered in Blender, and viewed in the UV Editor, this looks good (as above).

When I save it externally, it looks awful (both in Gimp and when re-imported back to Blender). I have tried various image formats (PNG, TGA, EXR).

PNG is terrible:

enter image description here

enter image description here

EXR has given me the best results. I've used the maximum depth that Blender gives me the option for, and turned off compression. Sometimes this makes a difference, but mostly it looks the same.

This is the most faithful version that I was able to achieve, but it's still pretty rubbish compared to the original.

enter image description here

[IMAGE]

I am aware of this answer. I suspect that this might be my problem, however, if it is, I would have expected the problem to only be present when the image is viewed in an external program.

I actually want to use this image back in Blender (in a different Blend file).

How can I save this image in a way that I can re-import it back into Blender (different .blend file) and have it look the same?

Lewis
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    https://blender.stackexchange.com/questions/72793/how-do-you-apply-colormanagement-settings-to-exr-files https://blender.stackexchange.com/questions/173932/exr-color-difference-to-png – Timaroberts Dec 09 '20 at 08:58
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    Use exr multilayer for further comp inside of blender. It skips the view transform, therefore appears different. Once back in blender it can use proper color management. – Timaroberts Dec 09 '20 at 09:04
  • Perfect, I understand now - thank you. PNGs aren't capable of what I want. EXRs can store the information externally, but are saved without colour management - so you need to apply some wherever you are using it (be that Blender or elsewhere). Just tested it and it works. Thank you! – Lewis Dec 09 '20 at 10:46
  • Only thing i will mention is that Multilayer EXR didn't work, I had to select simply OpenEXR. Multilayer saved OK, and I could see the image in the UV Editor when re-importing, however, it would not display when used in a material. Not sure why, but doesn't seem to matter. – Lewis Dec 09 '20 at 10:47
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    @Timaroberts You seem more skilled than me about PNG / EXR / transparency issues. This question made me discover odd behaviour: in 2.91, rendering fire over transparent background and adding Glow, the render looks good in Image Editor. Saving as PNG looks poor, but that's what I expected. Saving EXR and importing it back again looks good. However, the backdrop in the _Compositor looks poor as the PNG. So you can't preview what the EXR image output would look like - is there a way to change the backdrop preview? In 2.83.5 Compositor Backdrop and Image Editor both looked the same (poor). – Gordon Brinkmann Dec 09 '20 at 13:13
  • Use a black background to evaluate the image. Supposedly the issue with associated alpha on the rendered image viewport was fixed in 2.91. – susu Dec 09 '20 at 18:57
  • @Lewis bringing an exr back into blender would normally be done in the compositor for further work in comp. Do I misunderstand that you want to further work on the image? – Timaroberts Dec 09 '20 at 19:47
  • @Gordon multilayer is useful for working with the renderlayers directly as otherwise will collapse to the combined pass. png is just a bad format in general and should be avoided for this kind of thing altogether. – Timaroberts Dec 09 '20 at 19:47
  • @Timaroberts I know that PNG is a bad format for this, I was just wondering if there is no way to preview in Compositor how the render would look like. Even just viewing the EXR in the Image Editor shows a different image then the Render Result. Why can't Blender display an EXR like it displays the EXR when it's connected to the render composite output? – Gordon Brinkmann Dec 09 '20 at 21:38
  • @susu Yes, using the EXR with an Alpha Over node on a non-transparent background is what I usually do or viewing as RGB instead of RGBA. It just bothers me that Blender doesn't seem to be capable of displaying an EXR the same way as in the render composite. – Gordon Brinkmann Dec 09 '20 at 21:41
  • @Timaroberts I actually want to use it as a static image on a plane. No compositor involved. So I want a fire for my fireplace. I can create it using blender physics engine, but I can't export that and upload to Sketchfab. So I am basically creating a picture of fire. What you suggested works. When used in a material, the imported EXR is adjusted by the colour management settings and looks correct. – Lewis Dec 09 '20 at 22:07

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