gen-briefly-explain-the-circle-of-confusion-and-one-common-misco-c6a6

Briefly explain the circle of confusion and one common misconception about it.

## Circle of Confusion The **circle of confusion** (CoC) is the largest blur spot that still appears acceptably sharp to the human eye in a photograph. When a point of light is out of focus, it projects as a small circle rather than a point on the camera's sensor. The CoC defines the threshold where this blur becomes noticeable, and it's fundamental to calculating depth of field—the zone of acceptable sharpness in an image. ## Common Misconception Many people mistakenly believe the circle of confusion is a fixed, universal value. In reality, **CoC depends on viewing conditions**—particularly the final print size and viewing distance. A standard CoC of 0.03mm for full-frame cameras assumes an 8×10 inch print viewed from 10 inches away. If you're making a large wall print or allowing for heavy cropping, you'd need a smaller CoC value to maintain sharpness, which would reduce your depth of field. This is why the same lens at the same settings might appear "sharp enough" for web use but soft when viewed in a large print.