Permissible circle of confusion

DEFINITION:

A limiting circle of confusion within which a spot image can be identified as a spot in the photo lens, etc.

DESCRIPTION:

The range of sharpness of an image (picture) is determined by taking the resolving power of the human eye into consideration. A circle of confusion within the limit where the image is actually perceived as sharp is called the permissible circle of confusion (equal to or similar to the minimum circle of confusion). In commonly used photo lenses, the basis used to calculate the depth of field, hyperfocal distance, etc. is generally 1/30mm for a 24x36mm format or 1/20mm for a 6 x 6 cm format.