Minolta SR mount is the same bayonet as MC & MD but with no meter coupling or smallest aperture lever.
I know I can buy a bellows, either an old M42 or a new really expensive Novoflex, but that’s no fun. Besides, this one was too beat up to use as-was, so it was either repair/modify it or recycle the aluminum and landfill the rest.
There wasn’t much room for captions in the video and they go by pretty fast so here are the 1st pass results for how much magnification I get with the 75mm enlarger lens:
Bellows retracted all the way: 0.66… (2/3).
Bellows fully extended: 1.92.
The test shots were done on a full-frame Sony A7. Full-frame is 24mm high X 36mm wide. I just tested vertically and took photos of a ruler and counted the visible millimeters. 24mm would be 1:1 (life size). It’s not terribly accurate since I had the camera & bellows angled on a tripod and hand held the ruler but close enough for a go-no go check.
I’ll add images and more rigorous test results or link to a new post if it gets too long.