I have a quick question about the Mamiya 645 Super. The camera has a film back where one sets the ISO.
Does the ISO setting on the film back affect the light meter? In other words, if I change the ISO on the film back from 400 to 800, does the light meter know that I am using more light-sensitive film and adjust accordingly?
As long as everything is working, yes, the ISO dial changes the meter accordingly. You can try it by keeping everything still and pointed to the same scene and change the ISO.
The ISO setting on the film back is what makes it easy to switch back and forth between different films.
There is, of course, no ISO setting on the camera body itself .
The meter communicates with the back through electrical contacts on the back and body. It is important to keep those contacts clean and un-damaged.