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The image circle is the cross section of the cone of light transmitted by a
''Applied Photographic Optics''
3rd ed. Oxford: Focal Press
The image circle is the cross section of the cone of light transmitted by a lens
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'' ...
or series of lenses onto the image plane. When this light strikes a perpendicular target such as photographic film or a digital camera sensor, it forms a circle of light – the image circle. Various sensor aspect ratios may be used which all fit inside the same image circle, 3:2, 4:3, 16:9, etc.
A lens to be used on a camera that provides movements must have an image circle larger than the size of the image format (Adams 1980, 54). To avoid vignetting
In photography and optics, vignetting is a reduction of an image's brightness or saturation toward the periphery compared to the image center. The word '' vignette'', from the same root as '' vine'', originally referred to a decorative bor ...
, a photographer using a view camera
A view camera is a large-format camera in which the lens forms an inverted image on a ground-glass screen directly at the film plane. The image is viewed and then the glass screen is replaced with the film, and thus the film is exposed to exa ...
must ensure that the area remains within the image circle (Adams 1980, 56–57; 151–52; 157–61); a tilt/shift lens or perspective-control lens used on a small- or medium-format camera usually has mechanical limitations that keep the frame area within the image circle.
See also
* Film format *Image sensor format
In digital photography, the image sensor format is the shape and size of the image sensor.
The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular sensor. Because the image se ...
*Format factor
In digital photography, the crop factor, format factor, or focal length multiplier of an image sensor format is the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital ca ...
References
* Adams, Ansel. 1980. ''The Camera''. The New Ansel Adams Basic Photography Series/Book 1. ed. Robert Baker. Boston: New York Graphic Society. * Ray, Sidney F. 2000. The geometry of image formation. In ''The Manual of Photography: Photographic and Digital Imaging'', 9th ed. Ed. Ralph E. Jacobson, Sidney F. Ray, Geoffrey G. Atteridge, and Norman R. Axford. Oxford: Focal Press. * Ray, Sidney F. 2002''Applied Photographic Optics''
3rd ed. Oxford: Focal Press
Further reading
* Langford, Michael J. ''Basic Photography'', 3rd ed, 63–64. Garden City, NY: Amphoto, 1973. * Ray, Sidney F. ''Photographic Lenses and Optics'', 125. Oxford: Focal Press, 1994. * Stroebel, Leslie. ''View Camera Technique'', 3rd ed, 62–67. London: Focal Press, 1976. Photographic lenses {{photography-stub