If you are talking in the context of feeding a Blu Ray Player's signal into an older TV , the 1080p is probably not a supported mode. You should set the Blu Ray output to 720p , the sets native resolution or set the blue ray to 1080I and compare. Not to worry , Im sure either setting will look very good.
720 p/1080 p combatibility.....
How do you know if a 720p set accepts a 1080p signal?...manual says 1080i but no mention of 1080p format...set has hmi connections...sony kds 50e2000