Quick answer: Unreal RenderTarget format R8 producing washed-out tone? Default R8 is linear; tonemapping assumes sRGB - explicitly mark as sRGB or use R8 RGB sRGB format.
Cinematic post-process renders to a R8 target. Output looks crushed; comparing to the source shows lost tonal range.
Use B8G8R8A8_sRGB
RT format with explicit sRGB. Tonemapping pipeline matches expectations.
Or convert in shader
Sample as linear; output to sRGB via pow(color, 1/2.2) before final write.
Audit RT formats
Project's RT format list. Each format's color space documented; mismatches diagnose tone issues.
“Color space is a property of the format. Implicit color space = silent corruption.”
If your tone looks off, the format is the first thing to check. The tonemapper assumes a specific space; mismatch is the issue.