Unexpected behaviour when using Combine RGBA


I have spent some time trying to resolve this problem but I keep getting more and more confused. I stumbled upon this issue when converting and exporting normal maps for a game.

The basic problem I have can be reproduced like this:

  1. Create a new scene
  2. Open the node view, enable nodes
  3. Create a Combine RGBA node and set R, G and B to 0.5. (Keep alpha at 1.)
  4. Connect the Combine RGBA node to either a file output or a Composite node.

What I would expect is to get an image that has RGB=(127,127,127) everywhere.
However, I do get an image with RGB=(188,188,188) - which confuses me greatly and makes all the normals in my normal map point towards an incorrect direction.

I guess blender is applying some sort of color conversion before displaying or saving the file but I have found no mention of this in the documentation. I am using Version 2.71-2 on Arch linux. Any help is greatly appreciated!

Thank you!


Guessing that it’s doing some kind of gamma calculation, but seems odd.

It’s 0.5 in linear space but gets color managed values for the output. You could turn that off in scene properties -> color management.

Disabling color management did indeed fix it. I was not aware that blender does color management before. Thank you!