One of Canon's most popular wide-angle lenses - 17-40 mm f/4 L retrofocus zoom lens.

A wide-angle photograph of steps showing the perspective distortion due to the distance at which the picture is taken. In Photography and Cinematography, perspective distortion describes one of two phenomena – the appearance of a part of the subject as abnormally large relative The front stairs appear to tip forward.

In photography and cinematography, a wide-angle lens is a lens whose focal length is substantially shorter than the focal length of a normal lens for the image size produced by the camera, whether this is dictated by the dimensions of the image frame at the film plane for film cameras (film format)^[1] or dimensions of the photosensor for digital cameras. Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing See also Filmmaking Cinematography (from Greek: kinesis κινησις (movement and grapho γραφω (to record is the discipline A photographic lens (also known as objective lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light. In Photography and Cinematography a normal lens is a lens that generates images that generally look "natural" to a human observer under normal A film format is a technical definition of a set of standard characteristics regarding image capture on Photographic film, for either stills or movies Digital photography is a form of Photography that utilizes Digital technology to make Digital images of subjects

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 digital photosensor. In cinematography, a somewhat longer lens is considered "normal". ^[2]

There is an easy formula for calculating the angle of view for any lens that produces a rectilinear image. In Photography, angle of view describes the angular extent of a given scene that is imaged by a Camera. In addition to giving a wider angle of view, the image produced by a wide-angle lens is more susceptible to perspective distortion than that produced by a normal lens, because they tend to be used much closer to the subject. In Photography and Cinematography, perspective distortion describes one of two phenomena – the appearance of a part of the subject as abnormally large relative

Wide-angles lenses for 35 mm format

For a full-frame 35 mm camera with a 36 mm by 24 mm format, the diagonal measures 43. A camera is a device used to capture images either as still Photographs or as sequences of moving images ( Movies or Videos. 3 mm and by custom, the normal lens adopted by most manufacturers is 50 mm. Also by custom, a lens of focal length 35 mm or less is considered wide-angle.

Common wide-angle lenses for a full-frame 35 mm camera are 35, 28, 24, 21, 18 and 14 mm. A camera is a device used to capture images either as still Photographs or as sequences of moving images ( Movies or Videos. Many of the lenses in this range will produce a more or less rectilinear image at the film plane (though some degree of barrel distortion is not uncommon here). In Photography, a rectilinear lens is a Photographic lens that yields images where straight features such as the walls of buildings appear with straight lines as

Extreme wide-angle lenses that do not produce a rectilinear image are called fisheye lenses. In Photography, a fisheye lens is a Wide-angle lens that takes in an extremely wide hemispherical image Common focal lengths for these in a 35 mm camera are 6 to 8 mm (which produce a circular image). A camera is a device used to capture images either as still Photographs or as sequences of moving images ( Movies or Videos. Lenses with focal lengths of 14 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 12 mm, including zoom lenses with ranges of 2:1 that also begin at 12 mm.

Digital camera considerations

Apparent focal length in APS-sized digital cameras is increased by a crop factor. In Digital photography, a crop factor is the ratio of the dimensions of a camera's imaging area compared to a reference format most often this term is applied to

Most interchangeable-lens digital cameras today (2007) are in the form of 35 mm cameras. However, most of these cameras have photosensors that are smaller than the image apertures of full-frame 35 mm cameras. ^[3] For the most part, the dimensions of these photosensors are similar to the APS-C image frame size, i. Advanced Photo System ( APS) is a Film format for still Photography. e. , approximately 24 mm x 16 mm. Therefore, the angle of view for any given focal length lens will be narrower than it would be in a full-frame camera because the smaller sensor "sees" less of the image projected by the lens. The camera manufacturers provide a crop factor (sometimes called a field-of-view factor or a focal-length multiplier) to show how much smaller the sensor is than a full 35 mm film frame. In Digital photography, a crop factor is the ratio of the dimensions of a camera's imaging area compared to a reference format most often this term is applied to For example, one common factor is 1. 5 (Nikon DX format and some others), although many cameras have crop factors of 1. 6 (most Canon DSLRs), 1. 7 (the Sigma DSLRs) and 2 (the Four-thirds-format cameras). The 1. 5 indicates that the angle of view of a lens on the camera is the same as a 35 mm full-frame camera with a focal length of 1. 5 times the focal length, which explains why the crop factor is also known as a focal-length multiplier. As examples, a 28 mm lens would produce on the DSLR the angle of view of a 42 mm lens (given a crop factor of 1. 5) on a full-frame camera. So, to determine the focal length of a lens for a digital camera that will give the equivalent angle of view as one on a full-frame camera, the full-frame lens focal length must be divided by the crop factor. For example, to get the equivalent angle of view of a 28 mm lens on a full-frame 35 mm camera, from a digital camera with a 1. 5 crop factor, one would use an 18 mm^[4] lens.

Lens manufacturers have responded to this problem 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.

Construction

Cross-section of a typical short-focus wide-angle lens.

Cross-section of a typical retrofocus wide-angle lens.

There are two different varieties of wide-angle lens: short-focus lenses and retrofocus lenses.

Short-focus lenses are generally made up of multiple glass elements whose shapes are more or less symmetrical in front of and behind the diaphragm. As the focal length decreases, the distance of the rear element of the lens from the film plane or digital sensor also decreases. This makes short-focus wide-angle lenses undesirable for single-lens reflex cameras unless they are used with the reflex mirrors locked up. The single-lens reflex (SLR Camera uses an automatic moving mirror system which permits the photographer to see exactly what will be captured by the film or digital imaging Short-focus lenses are widely used on large format view cameras. Large format describes large Photographic films large cameras View cameras (including Pinhole cameras and processes that use a film or digital sensor The view camera is a type of Camera first developed in the era of the Daguerreotype and still in use today though with many refinements

The retrofocus lens solves this proximity problem through an asymmetrical design that allows the rear element to be further away from the film plane than its effective focal length would suggest. (See Angenieux retrofocus. The Angénieux retrofocus Photographic lens is a Wide-angle lens design that uses an inverted telephoto configuration ) 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 single-lens reflex (SLR Camera uses an automatic moving mirror system which permits the photographer to see exactly what will be captured by the film or digital imaging

References and notes

See also

• Anamorphic lens
• Angle of view for an example of an image taken by a wide-angle lens
• Panoramic photography
• Scioptric ball
• Image stitching
• Telephoto lens