[hank808]

It was on film, probably 35mm. That film contains more information than 4k video. Resolution is between 4K and 6K.

[MBCook]

Plus it’s a black & white movie, and b&w film has a higher “resolution” than color too right? Because you’re dealing with silver particles instead of physically larger color grains.

Or something like that. Someone more in the know please check my math.

[stevedh]

It was shot in colour. But the rest of the comments in the tree apply.

[reaperducer]

It's not in black and white.