I have to come clean here and say that I've succumbed to one of TV's soap opera's of sorts. Downton Abbey.There are many sites in which the observant have picked up historical gaffes such as curbs painted yellow to indicate parking spaces, roof antennae, modern watches, etc. Last week there was a scene in which there was a wedding photographer. In it he takes a picture of of the bride to be and two of the bridesmaids - the focusing hood over his head and flash powder.
As far as I know, the procedure with a ground glass type camera was the same in 1920 as it is today (in short); You compose and focus the shot (with the focusing cloth over your head and camera back). You take the cloth away from the camera and your head, you put in the plate/film holder in the back of the camera. Close the camera lens. adjust it's aperture and shutter speed. Pull the dark slide. Observe your subject and trigger the shutter with a cable release or some such device.
This procedure is almost unchanged even using today's high end digital and scanning backs with view cameras - albeit a bit more automated. In any case no photographer is ducking under a hood when he takes a picture.