Circle of Confusion Calculator

About this calculator

The circle of confusion (CoC) is the largest blur spot the human eye accepts as a sharp point in a final print or screen image — it's the reference value every depth-of-field and hyperfocal-distance formula is built on. It's approximated from a sensor's diagonal divided by a viewing-condition constant, commonly around 1500 for critical sharpness or 1442–1730 depending on the standard used, so a full-frame sensor (43.3mm diagonal) lands near 0.029mm while a Micro Four Thirds sensor (21.6mm) lands near 0.015mm.

Because CoC scales with sensor size, the same aperture and focal length give visibly different depth of field on different formats — which is exactly why a full-frame f/2.8 shot looks shallower than an equivalent APS-C or Micro Four Thirds shot. Cinematographers, photographers, and lens and camera manufacturers use the CoC value for a given sensor to compute accurate depth-of-field tables, hyperfocal distances, and focus-pulling marks.