[periheli0n]

You will notice that most of the photopgraphs have been made in direct sunlight. So he could have used high aperture and short shutter time. Most likely it was a fixed-aperture and shutter setup, since he could hardly have adjusted anything while shooting covertly. Still, not all of the photos are sharp, some do have motion blur, and some have grain, perhaps from pushing during development (i.e. correcting slightly underexposed shots).

But the technical basis was definitely on top of the game at the time, under the given conditions.