What is the circle of confusion?

The circle of confusion (CoC) is the largest blur spot on the sensor that still appears as a point to the viewer. Points smaller than the CoC look sharp; larger ones look blurred. It depends on sensor size, print size and viewing distance. Standard values: 0.029mm (full frame), 0.019mm (APS-C), 0.015mm (MFT).

How does CoC affect depth of field?

A smaller CoC means stricter sharpness criteria, resulting in shallower calculated DOF. Using the standard CoC gives traditional DOF values. For critical work (large prints, pixel-peeping), use a smaller CoC. The standard CoC assumes an 8x10 print viewed at 25cm.

Should I use a custom CoC?

If you regularly make large prints or view images at 100% on screen, the standard CoC may be too generous. For a 60cm print viewed at 50cm, calculate a custom CoC. For web-only images or small prints, the standard CoC is conservative enough.

How is the standard CoC calculated?

The traditional formula divides the sensor diagonal by 1500: CoC = diagonal / 1500. This assumes the final image is viewed as an 8x10 inch print at 25cm distance by a person with normal visual acuity (resolving about 5 line pairs per mm at 25cm).

PhotoCalcs

Circle of Confusion Calculator — CoC for Your Sensor

Calculate the circle of confusion for your sensor size, print size and viewing distance.

Sensor Size

Print Long Side

Print size for custom CoC

Viewing Distance

Distance viewer stands from print

How We Calculate This

Standard CoC

CoC = sensor diagonal / 1500

Custom CoC

CoC = (visual acuity blur on print) / enlargement factor

Visual acuity blur ≈ 0.2mm at 25cm, scaling linearly with distance.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.