Hi

I am doing some 10x8 macro transparencies ... which cost basically £40 a sheet film and process here in England
thankfully somebody else is paying but still every sheet counts
I could bracket +/- 1/3rd but that would probably push the budget over the edge and they would revert to digital which nobody wants

so what I would like to know is how do I calculate exactly

I have the math but where would I measure extension from
its from optical centre to film plane but how do i know where the optical centre is and then the film plane
after quite extreme movements is all over the place
4 corners of front and rear standards have probably +/- 10cm difference
obvious answer is to just average but is there a precise way

The transparencies will be displayed on light boxes so they need to be as near perfect as possible


best

robin