I looked at this a while ago, at the time photos had to be long exposures, several minutes. So if someone was walking along the roady, they would ‘blur’ into the road. and it like the reason the two people weren’t blurry was because one of the people was having their shoes shines by the other.
Is the glass:- Half full? Half empty? Twice as big for redundancy and margin of error? Twice as big but needs to be and has to go into the pressure cooker? …