出典:Wikipedia
出典:『Wikipedia』 (2011/01/02 06:53 UTC 版)
The image circle, or circle of illumination, of a lens is the circular area in the image plane formed by the cone of light transmitted by the lens (Ray 2000, 49). Within this circle is the smaller circle for which image definition is acceptable, the circle of good definition (Ray 2000, 49); however, some authors (Adams 1980, 54) make no distinction between the two. The covering power or coverage of a lens is often used interchangeably with image circle or circle of good definition (Adams 1980, 54; Ray 2002, 135), and relates to the size of the image format for which the lens provides acceptable definition; the covering power is sometimes given as an angle of view.