Clandestine 16mm movies.
I used to surreptitiously take 16mm movies. The only fixed variable was the shutter speed. From there on we had depth of field issues including focus, ape, and film speed issues. Along with that came screwing various lenses on and off, all of that being done at various times of the day and night.
One lens I had was 16" long, weighed enough that I had a camera mounted on a rifle stock and still had to cushion it. Even if, with the adrenaline flowing, you could hold it absolutely still, your heartbeat would show up.
All of that had to be done with the pressure to keep activity in sight, yourself out of sight, and move with them.
How much easier it would be with today's digital stuff.