Circle of Confusion Calculator — CoC for Your Sensor

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).

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.

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.

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.