Question: are criterion blu rays 4k?
Answer: Criterion does not release 4K (UHD) discs, they release Blu-ray (1080p) and DVD (720p) discs, but in some cases the film itself was remastered/restored at 4k beforehand. This means they scanned the original film into a computer at 4k resolution and then converted it to 1080p/480p for their disc.