Fisheye (lens)

"Circular" fish eye "Fish-Eye Nikkor 2.8 / 6" with a camera " Nikon F2 Photomic"

Priority in ultra-wide-angle photography using hand-made optics, like the term fish eye itself , belongs to the well-known American experimental physicist Robert Williams Wood , who published the results of his experiments in this field in 1906 ^{[5] [6]} .

The practical use of the effect began in the 1920s, when lenses of this type were developed for shooting clouds in meteorology . One of the first samples was the "Hill Sky Lens", made in 1924 by the London company Beck of London ^[7] . The lens gave an image in the form of a circle and allowed one shot to shoot the entire celestial hemisphere. In the USSR, Vladimir Churilovsky in 1933 proposed the technology of aerial photography with a distorting lens, covering a large area of ​​the terrain. To decode the obtained images in the form of a circle, an orthotransformer with the same distortion as the lens, but with the opposite sign was used ^[8] .

Subsequently, distorting lenses were widely used in photojournalism , photo art and cinema as an expressive tool. Spherical cinema systems (for example, IMAX DOME ) are also based on the use of fisheye lenses for shooting and projecting images onto a hemispherical screen ^[9] . Due to the shape of the screen, the distortions inherent in such optics are compensated and viewers observe objects in a normal perspective at large angles that enhance the presence effect ^[10] .

Fisheye lenses are usually divided into two main varieties according to the degree of filling the camera’s frame window: circular and diagonal ^[3] .

• Circular - in this case, the circle of the image field provided by the lens does not fill the entire frame window, and its diameter is close to the size of the short side of the frame. Such a lens has a field of view angle of 180 ° or more in all directions. For a small format frame, the focal length of the circular fisheye is usually 6-8 mm, which is almost five times less than the required posterior segment when used with a single-lens reflex camera . Therefore, the optical design includes three powerful negative menisci in the front part, leading to the weighting of the entire device ^[3] . Often the dimensions of circular lenses, due to the large diameter of the front lenses, exceed the dimensions of the camera several times ^[11] . They found the most widespread use in special fields of applied photography, for example, in meteorology for shooting the sky . Examples of circular features:
  • "Sigma AF" 8 mm f / 3,5 EX DG FISH-EYE;
  • " MS Bearing " 8 mm f / 3.5;
  • " Nikkor " 6 mm f / 2.8 ^[11] ;
  • “Sigma” 4.5 mm f / 2.8 EX DC Circular Fisheye HSM - for digital cameras with APS-C sensor ;
  • Zenitar 8 mm f / 3.5 (for Canon EF and Nikon F mounts) ^[12]

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  Shot of the ship “ Academician Ioffe ”

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  Snapshot of the space shuttle Atlantis

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  Night shot of the celestial hemisphere

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  Street shot
  Circular lens

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  Interior. Diagonal Lens

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  Car interior
  "Diagonal" lens

• Diagonal (or “full-frame”) - the received frame is entirely occupied by the image cut out from the round spot provided by the lens. The angle of view 180 ° corresponds to the diagonal of the frame. For a small format frame, the focal length of such a lens is usually 16 mm, and for a medium format 6 × 6 cm, 30 mm ^[3] . Examples of lenses of this type:
  • Canon EF 15 mm F / 2.8 Fish-eye
  • " MS Zenitar-M "

With a very wide angle of view, strong perspective distortions inevitably arise: the background seems farther than it actually is, and when moving away from the center of the field of view, the shape of objects is distorted. When creating orthoscopic wide-angle lenses, they try to reduce distortion to zero - the curvature of straight lines that do not pass through the center. However, in this case it is fundamentally impossible to obtain a field of view angle of 180 °, since then the edge of the field of view will be infinitely distant (the image provided by such a lens is equivalent to the gnomonic projection of a sphere onto a plane). In addition, the increase in the center is less than at the edge, which may be inconvenient in some shooting situations. Therefore, to achieve a field of view angle of 180 degrees or more, negative distortion (“barrel”) is intentionally introduced into the lens during its development. Then the increase in the center becomes larger, and in this area the lens works as a less wide-angle one. Nevertheless, such compensation introduces its own distortions of perspective - the protrusion of the center, and also leads to distortions in the shape of objects: straight lines (except for those passing through the center) are represented by curves.

A perspective similar to that created by fisheye lenses can be reproduced by gluing panoramas from photographs taken with orthoscopic optics. Most computer applications for gluing allow you to specify various projections of the final image, including stereographic .

• Planetariums are used to project images of the celestial sphere;
• In flight simulators for projecting the image of the surrounding space onto hemispherical screens. This allows you to strengthen the "immersion effect" for pilots , air traffic controllers and military specialists;
• In spherical cinema systems , such as IMAX DOME (OMNIMAX) or Speysarium, fisheye lenses are used for shooting and projection onto a hemispherical screen;
• In agriculture and forestry for measuring indices of land cover and insolation ;
• In astronomy, it is used to measure cloud cover and light pollution , as well as the fixation of auroras and traces from meteors ;
• In photography and cinema for shooting in very tight spaces and as an expressive means of photo reporting;
• Computer graphics use display laws similar to the fisheye perspective to simulate reflections in mirrored spherical surfaces;
• Most door peepholes are constructed according to the optical fisheye design for easy observation;
• The first music video , shot entirely with a fisheye lens, was created in 1987 on a Beastie Boys song ;

On fisheye lenses, the traditional installation of filters in front of the front lens ^{[* 2] is} not possible. The filters are installed behind the rear optical element, which complicates their operational change and makes their rotation impossible (which is necessary for gradient and polarization filters ). In addition, the lack of space behind the last optical component in single-lens reflex cameras with a moving mirror often leads to the inability to use filters in the frame due to its thickness. In these cases, a special holder for flat filters from a painted thin polymer film is provided on the back of the lens barrel . Older lenses of this type have built-in revolving discs with a standard set of yellow, orange and red filters for black and white photography. Attaching a lens hood to the lens is also impossible due to its inevitable vignetting of the visual field. Most diagonal lenses are equipped with a fixed lens hood integrated into the frame. However, due to its small size, this lens hood is ineffective.

• Borodulin, Lev Abramovich - the first photographer in the USSR who used a fisheye lens. ^[13]

• Fisheye (optical system)
• Zodiac (lens)
• Wide angle nozzle
• Panoramic photography

• D.S. Volosov . § 5. Wide-angle distorting lenses // Photographic optics. - 2nd ed. - M.,: "Art", 1978. - S. 329-333. - 543 p.

• Valery Tarabukin. Modern photo lenses (Russian) // " Soviet Photo ": magazine. - 1988. - No. 4 . - S. 42, 43 . - ISSN 0371-4284 .

• M. I. Shulman. Cameras / T. G. Filatova. - L.,: "Mechanical Engineering", 1984. - 142 p.

• Cinemas for cinema systems IMAX and OMNIMAX (Russian) // " Technique of cinema and television ": magazine. - 1983. - No. 10 . - S. 70-72 . - ISSN 0040-2249 .

• Soviet special cameras for aerial photography (Russian) // "Photocourier": magazine. - 2006. - No. 4/112 . - S. 22-28 .