Probably an "edge lit" model? (as opposed to full local dimming array) Look for a forum here for your specific model (55" TCL is too vague) for options to reduce the edge back lighting.
If part of what you are talking about is the darker areas in the blue seen on the Paramount logo photo you attached. This is a sort of "clouding" effect were you see random patches of darker and paler areas of the screen (do not confuse this with patterned patches of lighter/darker areas - that is most likely LED zones from the backlight).This has been driving me nuts ever since I noticed it few weeks ago. Does anybody have any guesses to what could be wrong with it? There is a weird outline around whole outside edges, it appears on all inputs and even just on tv menu itself. First pic you can see how its almost like a window around the actual pic all the way around,2nd pic shows edge right side.
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