for 100" would need to be < 13' (50" is 6'6") for 4k benefit, plus as he said viewing position -
for a led if you sat 8' away from a 100" it fills about 50 degree field, but brightness at edges 25% down and black level x3
for a led if you sat 8' away from a 100" it fills about 50 degree field, but brightness at edges 25% down and black level x3