I was experimenting a lot with multiple exposures on the same frame on film and noticed an unexpected behaviour. While this might very well have to do with my cameras shutter not working properly, it's been so consistent that I thought I'd ask the community if I am missing something.
I am using a Minolta camera from the 80s and I'm shooting on Fuji color reversal film. When I took two picture on one frame I noticed I could get away with taking two pictures at "normal settings" (as in: what I would set the camera to if I just took a single picture) on the same frame and it didn't really look awfully overexposed.
Now, when I took several pictures on one frame I figured I'd just double the shutter speed if I took two pictures or quadruple it to take four pictures and so on (I'd actually just multiply the film's iso by the number of exposures and set the camera to that value). Using that system, I noticed the more exposures I did on one frame the seemingly darker it became.
Am I missing something here? I thought evenly spreading exposure time over all exposures would be the same as having one exposure with the full time but maybe the film has some properties to it that defy that logic?
I'd be thankful for clarification.