Panasonic 50gt50 is the plasma i refer too. Its more like a cloudy dusty circular spot. like when you light a match to plastic you get the smokey effect before it burns. could be described has backlight but as pronounced . i did seem to disappear yeaterday evening but returned again this morning... But smaller. strange. Thi sis the second panel, and i have had it since jan 2013. it isn't effecting picture quality so i assume its on the screen itself..?