Finite Depth of Field Limit Calculator
Where are the near and far acceptable-blur limits in a stated thin-lens focus model?
Method, formula and assumptions
Use H = f^2/(N x c) + f. Near = H x s/(H + s - f), far = H x s/(H - s + f), all lengths in mm. This page supports only positive finite far limits, explicitly rejecting an unbounded result.
Input definitions and supported units
- Focal length (mm): Measured or assumed numerical value, from 0.1 to 2000; must be positive.
- f-number: Measured or assumed numerical value, from 0.1 to 128; must be positive.
- Chosen blur-circle diameter (mm): Measured or assumed numerical value, from 0.0001 to 1; must be positive.
- Focus distance (mm): Measured or assumed numerical value, from 1 to 100000000; must be positive.
Worked example with answer
50 mm, f/8, a chosen 0.03 mm blur circle and 3,000 mm focus distance give H = 10,466.6667 mm, near = 2,340.3727 mm and far = 4,177.3836 mm. Finite depth is 1,837.0109 mm.
How to use the results
The chosen blur circle defines 'acceptable', not a universal sharpness threshold. This complements measured focus-stack steps but does not substitute for them.
Results retain full precision internally and display up to four decimal places. Very small nonzero results use scientific notation rather than appearing as zero. Check the labels before comparing values across units.
Limitations and references
Thin-lens approximations, pupil magnification and focus-distance conventions limit accuracy, especially at macro distances. No sensor preset or professional sharpness criterion is claimed.
PhotoPills: depth-of-field calculator and definitions. Undated optical calculator checked October 11, 2026; blur-circle choice remains an explicit user input.
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