It's chemical exhaustion in your eyes behind the lens, they will exhaust to anything intense where luminosity or chroma (colour) and the resposne to that will drop, so it's masking + colour balancing somewhat. Open photoshop, and make one white layer, then a bright cyan layer above it, then full screen photoshop, stare at the cyan layer for 1 minute, turn it off, the white layer will not look white.
A 'fine detail mask' will just serve to cancel out (partially) the image. And will actually do the opposite of the results you wan't. It will not change the response of the film of a bright to dark area, that'll remain the same, but within the bright area, it's own contrast of fine details will be masked down,