With only sodium and fabric api:

Adding indium:

I don't see how this would be possible, Indium doesn't touch vignette rendering. Are you absolutely sure there are no differences other than Indium between the instances you took those screenshots in? Could you send the options.txt file after running the game each time?

It's the exact same fresh default settings instance for each screenshot with no other mods than those listed. options.txt is identical after each test run as well. It looks a bit like the vignette texture is being applied twice with indium enabled.

The vignette in vanilla takes ~10 seconds to adjust to the environment you're in, so if you'd only just loaded into the world it might not have had time to reset (it starts at full vignette when you load the game).