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), 0.014mm (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 (d/1500) CoC assumes a print of roughly 30cm diagonal — about an 8x10 inch enlargement — 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 d/1500 formula divides the sensor diagonal by 1500: CoC = diagonal / 1500. By convention this corresponds to a viewer with normal acuity resolving about 5 line pairs per mm at 25cm on a print of roughly 30cm diagonal (illustratively an 8x10 inch enlargement). For full frame this gives 43.3mm / 1500 ≈ 0.029mm.

PhotoCalcs

Circle of Confusion Calculator — CoC for Your Sensor

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

Sensor SizeCamera sensor format 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

The d/1500 convention assumes a viewer resolving ≈5 line pairs per mm at 25cm on a print of roughly 30cm diagonal (illustratively an 8×10 inch enlargement). Full frame: 43.3mm ÷ 1500 ≈ 0.029mm.

Custom CoC

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

Visual acuity blur ≈ 0.2mm at 25cm, scaling linearly with viewing distance. Enlargement factor = print diagonal ÷ sensor diagonal (3:2 print assumed).

Frequently Asked Questions

Related Calculators

DOF Calculator

Calculate near focus limit, far focus limit and total depth of field for any lens, aperture and subject distance combination. Free online calculator.

Hyperfocal Distance Calculator

Find the hyperfocal distance for maximum depth of field in landscape photography. Enter focal length, aperture and sensor size. Free online calculator.

Bokeh Calculator

Estimate background blur disc size for any lens, aperture and subject-to-background distance. Predict bokeh quality before you shoot. Free online calculator.

Focus Stacking Calculator

Plan focus stacking sequences for macro and landscape photography. Calculate the number of frames and focus step distance needed. Free online calculator.

Aperture Calculator

Find the exact aperture needed to achieve a target depth of field at any given focal length and subject distance. Free online photography calculator.

Last updated: February 2026

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