There are 2 competing '4K' sizes - one which is 4K pixels wide (4096x2160) and one which is double 1080p in either dimension (3840x2160), but not quite 4K pixels wide. Not sure which format 4K blu-ray uses, or how much difference a normal person would be able to spot either with scaling or chopping off the edges if content had to be reformatted between the two.
Biting the hand that feeds IT
