Camera was also a formidable instrument those days. It was a big box, a full load for a man to carry. The box was fitted on a tripod and the photographer adjusts the focus by adjusting the telescopic slide from behind. After this he will look up with a smile at the group sitting (or standing) in front of him.
"Ready, smile please" (just look at the one I have fitted on my face!). Then in a flash of second he will pull out the shutter. The thing is finished!