Ok, not to be contrary, but I want to do this completely differently.....

For me, since my mono-rail doesn't have a built-in ruler, I would find it much easier to just have a table for *subject distance*. I think I could accurately guesstimate subject distance better than bellows draw (image distance). Why does no one do this? Why is the sky blue?

Having a table divided by 1/3 stops would also be nice. So, if I have a row of desired exposure compensations (like 1.33, 1.66, 2, 2.66, etc... all the way up to 16 let's say, a.k.a 4 stops) and I know my focal length (180mm), I should be able to calculate for subject distance, right?

Can anyone do the algebra and concoct a singular formula? I was having to convert exposure compensation to magnfication and then to subject distance and at about 2 o'clock in the morning I was beginning to lose my patience.