If you’ve got a 40 inch TV and are thinking of upgrading to a 50 inch for a better wide-screen cinema effect why not just sit closer. For example, the recommended distance for viewing a 50 inch screen is 1.8m which is a viewing angle of 34 degrees but if you sit just 35cm closer to your 40 inch screen (1.45m) you will get the same result without having to spend any money!
For a 32 inch screen sit 1.15m away for the same result
For a 26 inch screen – sit 0.95m away for the same result
I think 1.5m is about as close as you can comfortably watch a TV from a settee so a 40 inch is about right for little me! You only need a bigger one if you’re going to invite all the neighbours round to watch football matches! Lol
The mathematical formula for working out the distance from the screen which provides a viewing angle of 34 degrees is:
=(COS(ATAN(9/16)) * DIAG /2)/TAN(RADIANS(34/2))
(where 34 is the viewing angle required, 16:9 is the standard wide screen ratio and DIAG is the screen size) but the quick way is to multiply the screen size (diagonal distance) by 1.4 which makes the recommended distance for a 40 in screen 56 inches or 142 cm which is about right (within an inch).