Acceptable circle of confusion
From The Glossary of Digital Photography
Refers to a circle of confusion that is small enough not to be noticeable in a photograph. For common types of photography, acceptable circle of confusion is set as the largest size of circle that will still be seen as a point when the image is displayed as an image with a 30-cm diagonal when viewed at a distance of 50 cm. If human vision acuity can distinguish five lines per millimeter at 25 cm, an accepted standard, then the largest acceptable circle of confusion would be .2 mm. These numbers would then have to be converted to the size of the digital sensor if the measurement were to be made at the sensor rather than at the final print size. See also circle of confusion
