Yep, understand the BF and inverse square concepts.

I'm just directionally dyslexic or something when it comes to mechanical stuff...I would probably apply the correction factor in the opposite way with my luck.

If I can do the math, I for some reason understand better and screw up less.

I want to explore a single step correction for distance change with flash analogous to bellows factor so I don't have to think about how many factors of two.

Flash for pinhole is one path here, and since the typical f-stop and distances one might move a flash to/from are unlikely to be 'clean' factors of 2 or square root of 2, I'm going to scratch my head some more. I use EV too so I don't care how where the math goes.

Thank you for the jump-start.

Murray