The inst. manual with my new flat screen tv warms against prolonged images in the 4:3 format. I assume it refers to the black bars on each side of the screen when watching something in that format. When I watch something thru Roku I typically get a black bar either on the side or top and bottom. If I "blow it up" to fill the screen I loose part of the picture. Old movies even on HD channels frequently have the bars on the sides. Am I really harming the tv watching these?