I did a lot of high magnification work, and had a calculator always at the ready.
Made a small computer program that did all the different calculations i need in one go.

A version of that program, tailored to Zeiss/Hasselblad lenses, is online.

Still want to port it to run on PDAs, but haven't gotten round to it.

Reciprocity failure is to 'unruly' to capture in a calculator.