Good question.... I've noticed this myself. Starts bright and slowly fades to greyish.I notice that when subtitles or credits come on (white with a black background), they are white at first then change to a grayish color. Sometimes, when there are two lines of subtitles on the screen at the same time, the top line is white and the bottom line only turns to the grayish color. Is this normal? Can any settings be changed to fix this?