circle of confusion calculator
        For a suitable general purpose circle of confusion for use in depth of field calculations, simply select your desired film format, leaving the paper size and resolution settings at 10"x8" and 5 lines/mm respectively. Make note of the calculated circle of confusion at the bottom left. Intermediate calculation results are also shown.

For more background information please refer to the 'Notes on Depth of Field'.

Film Format
Paper Size
Image Resolution

  Negative Paper Image
Aspect Ratio

Enlargement factor : (Image diagonal divided by the negative diagonal)
Resolution factor : (Enlargement factor multiplied by the resolution)
Circle of Confusion : (Reciprocal of the resolution factor)