Well I am a bit confused if the 55 and the 75 have the same peak brightness then will the 75 seem to less bright as the same is being watched over a larger distance ?And a 55" TV from 5.5 feet is going to look exactly as bright as 75" from 7.5 feet if they have the same brightness output. They'll fill in the same field of view and are exactly the same brightness. The 75" is further away, but since it's bigger it generates proportionally more light output.