Originally Posted by
ic-racer
You can calculate the optimum aperture for enlarging warped negatives, or curved field lenses, based on the focus spread (based on view camera focus equation of Hansma).
N = 20/(1+M) * square root of 'dv'
N = Aperture number
20 = user dependent constant (circle of confusion 0.15mm for me)
M = magnification
'dv' = millimeters of focal depth on the enlarger column.
Yes the optimum focal point is, for all practical purposes, in the middle point of the 'dv' or focal spread. Just like focusing a view camera. The 'dv' is obtained by moving the whole head up and down and recording the distance between sharp and blurry.
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