Peter, I believe gigabitfilm will improve the resolution of Minox camera lens by about 2 fold from 170 lpmm to about 300 lpmm(posted 8629 days ago)You probably don't know about microdot photography.
In 1925, Emmanuel Goldberg already developed a microdot camera capable of 500:1 reduction in one step. Later, in WWII, Zeiss microdot camerras were widely used. 500:1 in one step.