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In photography and cinematography, a wide-angle lens is a lens covering a large angle of view. Conversely, its focal length is substantially smaller than that of a normal lens for a given film plane. This type of lens allows more of the scene to be included in the photograph, which is useful in architectural, interior, and landscape photography where the photographer may not be able to move farther from the scene to photograph it.
Another use is where the photographer wishes to emphasize the difference in size or distance between objects in the foreground and the background; nearby objects appear very large and objects at a moderate distance appear small and far away.
This exaggeration of relative size can be used to make foreground objects more prominent and striking, while capturing expansive backgrounds.
A wide-angle lens is also one that projects a substantially larger image circle than would be typical for a standard design lens of the same focal length. This large image circle enables either large tilt & shift movements with a view camera.
By convention, in still photography, the normal lens for a particular format has a focal length approximately equal to the length of the diagonal of the image frame or Image sensor. In cinematography, a lens of roughly twice the diagonal is considered "normal".Anton Wilson, Anton Wilson's Cinema Workshop, American Cinematographer, 2004 (Page 100)
Another result of using a wide-angle lens is a greater apparent perspective distortion when the camera is not aligned perpendicularly to the subject: parallel lines converge at the same rate as with a normal lens but converge more due to the wider total field. For example, buildings appear to be falling backward much more severely when the camera is pointed upward from ground level than they would if photographed with a normal lens at the same distance from the subject because more of the subject building is visible in the wide-angle shot.
Because different lenses generally require a different camera–subject distance to preserve the size of a subject, changing the angle of view can indirectly distort perspective, changing the apparent relative size of the subject and foreground.
Ultra wide angle lenses have a focal length shorter than the short side of the film or sensor. In 35 mm, an ultra wide-angle lens has a focal length shorter than 24 mm.
Common wide-angle lenses for a full-frame 35 mm camera are 35, 28, 24, 21, 20, 18, and 14 mm, the latter four being ultra-wide. Many of the lenses in this range will produce a more or less rectilinear lens image at the film plane, though some degree of barrel distortion is not uncommon.
Ultra wide-angle lenses that do not produce a rectilinear image (i.e., exhibit barrel distortion) are called . Common focal lengths for these in a 35 mm camera is 6 to 8 mm (which produce a circular image). Lenses with focal lengths of 8 to 16 mm may be either rectilinear or fisheye designs.
Wide-angle lenses come in both fixed-focal-length and zoom varieties. For 35 mm cameras, lenses producing rectilinear images can be found at focal lengths as short as 8 mm, including zoom lenses with ranges of 2:1 that begin at 12 mm.
Lens manufacturers have responded by making wide-angle lenses of much shorter focal lengths for these cameras. In doing this, they limit the diameter of the image projected to slightly more than the diagonal measurement of the photosensor. This gives the designers more flexibility in providing the optical corrections necessary to economically produce high-quality images at these short focal lengths, especially when the lenses are zoom lenses. Examples are 10 mm minimum focal length zoom lenses from several manufacturers. At 10 mm, these lenses provide the angle of view of a 15 mm lens on a full-frame camera when the crop factor is 1.5.
This makes short-focus wide-angle lenses undesirable for single-lens reflex cameras unless they are used with the reflex mirrors locked up. On large format and rangefinder cameras, short-focus lenses are widely used because they give less distortion than the retrofocus design and there is no need for a long back focal distance.
retrofocus lens solves this proximity problem through an asymmetrical design that allows the rear element to be farther away from the film plane than its effective focal length would suggest. (See Angénieux retrofocus.)
For example, it is not uncommon for the rear element of a retrofocus lens of 18 mm to be more than 25 mm from the film plane. This makes it possible to design wide-angle lenses for single-lens reflex cameras.
The axial adjustment range for focusing Ultra wide angle lenses and some Wide-angle lenses in View camera is usually very small. Some manufacturers (e.g. Linhof) have offered special focusing lens mounts, so-called 'wide-angle focusing devices' for their cameras that allow the lens to be focused precisely without moving the entire front standard.
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