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I have a 32-bit EXR image that's supposed to show the following color:

r: 0.5
g: 0.5
b: 1.0

each color channel is in the [0, 1] range. When I open the EXR file in Photoshop, this is what I see:

enter image description here

You'll notice that the color picker accurately lists r: 0.5, g: 0.5, b: 1.0, but visually it's much lighter than it should be. A color of those values should look more purple, like this:

enter image description here

The problem is that I need to take the 32-bit EXR and convert to 8-bit PNG, but it's coming out much lighter than it should. Instead of getting the color I need #8080ff, I'm getting the lighter #bcbcff. Do I need to do gamma correction, or some sort of linear-space conversion? I believe this question is very similar to this question for GIMP, but that one doesn't have an answer either.

4
  • set working space to something linear
    – joojaa
    Commented Oct 17, 2020 at 6:42
  • @joojaa ok, how?
    – M -
    Commented Oct 17, 2020 at 6:43
  • Edit > Color settings. Unfortunately your unlikely to have a linear profile on your computer since no image ever is linear.
    – joojaa
    Commented Oct 17, 2020 at 6:46
  • When viewing a 32 bit image on a normal computer monitor in Photoshop, you can't see the full tonal range in the image, so basically what you are seeing on-screen is not fully representative of the colour information in the image. If you want to convert a 32bit image to PNG24 (i.e 8 bit per channel), you will have to tone map it in some way. See this page on the Adobe Support forum for more info.
    – Billy Kerr
    Commented Oct 17, 2020 at 9:37

1 Answer 1

-1

The only way I was able to convert a 32-bit .exr normal map into an 8-bit .png normal map is by opening a second file with 8-bit RGB mode and copy/pasting the individual channels.

Open the channels tab (next to Layers) and:

  • copy .exr red channel -> paste into .png's red channel.
  • copy .exr blue channel -> paste into .png's blue channel.
  • copy .exr green channel -> paste into .png's green channel.

Now you can see, the color that was 0.5, 0.5, 1.0 in the EXR file is now 128, 128, 255 in PNG, as desired: enter image description here

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