I'm also using computer 12.5-75/f1.2 and two cs-c mount adapter as you suggested, but I find it impossible to focus no matter how far or how close the camera is. Do I need to do some other adjustments? Thanks!
Problem with "Macro rings" is that, the depth of field or what is in focus is really small. Computer 12.5-75/f1.2 lens from the go have really tiny depth of field, stacking more cs-c adapters makes it shallow like caliper of paper. Additionally "macro rings" reduces light intensity of lens - f1.2 is no longer f1.2, but something lower.
For filming with confined space, or macro to be done, I'm using noname lens 2.8-12mm f/1.4 zoom, it is available in Krontech store.
It's focusing from 0mm! Yes you can focus on your fingerprint that is on front lens
https://www.krontech.ca/store.html#!/2-8-12mm-f-1-4-zoom-lens/p/77257270/category=21981409 Works like a charm
I'm using it only on 12mm side. If you're not scared of little light dropout on corners at full resolution it's great lens.
Some test films made with 2.8-12mm f/1.4 zoom:
https://www.youtube.com/watch?v=3RSyc4McGewhttps://www.youtube.com/watch?v=X_JRrJrup5shttps://www.youtube.com/watch?v=l1i-fhH1gD0And it's CS mount lens, you have to use it without 5mm CS-C adapter, or you will have -∞ mm focusing depth, and black hole will emerge
Best Regards,
Marcin