@paintevil hi Timo, good question! Post processing with Blenders compositing is fully allowed, it’s in Blender so go wild 😊
Other software like Photoshop, Gimp or Krita, only minimal post processing. Removing fireflies, bit of sharpening, basic color correction. Nothing too crazy that alters the render completely. It should still look like what you made with Blender.
I added this clarification to the challenge description at the top.
Hope this makes sense, and looking forward to what you can do! 😎👍🏻