Quote Originally Posted by polyglot View Post
Q3: time. Again, this is often not the easiest way to arrive at the answer you want because you probably cannot measure the image distance. For me at least, I generally start the bellows compensation calculation from magnification (M = image size / object size). And if you've computed exposure using effective f-number instead of marked f-number, you've already performed this correction.
Sometimes even guessing magnification ratio is not that easy. Therefore I made an excel sheet for all lenses I had.
Expositon Compensation Chart.png
All I need is to focus, measure distance between standards and find a nearest compensation factor. E.g. if the distance between standards after focusing Symmar 150/5.6 is 200mm, I have to expose more by 1 1/3 EV. Row '3' values (distance when focused on infinity) was measures, the rest are calculated.