I do a lot of 1:1 projection printing of 8x10 negatives.
This is how the numbers work out. (but you can easily check 'dv' for yourself by moving the column up and down)
N = 20/(1+M) * square root of 'dv'
N = Aperture number
20 = constant (circle of confusion 0.15mm)
M = magnification
'dv' = millimeters of focal depth on the baseboard.
So, for me a 1:1 enlargement works out like this:
f16 = 20/2 x square root 'dv'
f16 = 10 x square root 'dv'
'dv' = 2.56mm
Again, enough focal depth for any paper out there.
This is a real-life situation. If you substitute other hypothetical numbers (ie smaller f-number and smaller acceptable CoC, then you may approach a number small enough that paper height comes in to play)
Now, if you do reductions, then the story is different.
One of these days I'm going to try to compare 8x10 to 4x5 reductions to 4x5 to 4x5 contact prints. I predict paper thickness my need to be considered, but when I do it, I'll post my empiric results.
Last edited by ic-racer; 04-26-2009 at 01:07 PM. Click to view previous post history.