Fisheye Lens

Fisheye lenses also have other applications, such as re-projecting images originally filmed through a fisheye lens, or created via computer-generated graphics, onto hemispherical screens. They are also used for scientific photography, such as recordings of aurora and meteors, and to study plant canopy geometry, and to calculate near-ground solar radiation. In everyday life, they are perhaps most commonly encountered as peephole door viewers to give a wide field of view.

Panoramas with fisheye distortion predate photography and the fisheye lens. In 1779, Horace Bndict de Saussure published his downward-facing fisheye view of the Alps: "All the objects are drawn in perspective from the centre".[8]

Fisheye Lens

Download 🔥 https://tlniurl.com/2y4It9 🔥

In 1906, Wood published a paper detailing an experiment in which he built a camera in a water-filled pail starting with a photographic plate at the bottom, a short focus lens with a pinhole diaphragm located approximately halfway up the pail, and a sheet of glass at the rim to suppress ripples in the water. The experiment was Wood's attempt "to ascertain how the external world appears to the fish" and hence the title of the paper was "Fish-Eye Views, and Vision under Water".[1] Wood subsequently built an improved "horizontal" version of the camera omitting the lens, instead using a pinhole pierced in the side of a tank, which was filled with water and a photographic plate. In the text, he described a third "Fish-Eye" camera built using sheet brass, the primary advantages being that this one was more portable than the other two cameras, and was "absolutely leaktight".[1] In his conclusion, Wood thought that "the device will photograph the entire sky [so] a sunshine recorder could be made on this principle, which would require no adjustment for latitude or month" but also wryly noted "the views used for the illustration of this paper savour somewhat of the 'freak' pictures of the magazines."[1]

W.N. Bond described an improvement to Wood's apparatus in 1922 which replaced the tank of water with a simple hemispheric glass lens, making the camera significantly more portable. The focal length depended on the refractive index and radius of the hemispherical lens, and the maximum aperture was approximately f/50; it was not corrected for chromatic aberration and projected a curved field onto a flat plate. Bond noted the new lens could be used to record cloud cover or lightning strikes at a given location.[2] Bond's hemispheric lens also reduced the need for a pinhole aperture to ensure sharp focus, so exposure times were also reduced.[10]

The Hill Sky Lens was fitted to a whole sky camera, typically used in a pair separated by 500 metres (1,600 ft) for stereo imaging, and equipped with a red filter for contrast; in its original form, the lens had a focal length of 0.84 in (21 mm) and cast an image 2.5 in (64 mm) in diameter at f/8.[13] Conrad Beck described the camera system in an article published in 1925.[14] At least one has been reconstructed.[15]

The AEG Weitwinkelobjektiv formed the basis of the later Nippon Kogaku (Nikon) Fisheye-Nikkor 16 mm f/8 lens of 1938, which was used for military and scientific (cloud cover) purposes.[17][19] Nikon, which had a contract to supply optics to the Imperial Japanese Navy, possibly gained access to the AEG design under the Pact of Steel.[19]

At approximately the same time that Schulz was developing the Weitwinkelobjektiv at AEG, Willy Mert [de] at Zeiss was developing the Sphaerogon, which was also designed to encompass a 180 field of view.[22][23] Unlike the Weitwinkelobjektiv, Mert's Sphaerogon was not limited to medium format cameras; prototype versions of the Sphaerogon were constructed for the Contax I miniature format camera. The first prototype Sphaerogon lenses constructed had a maximum aperture of f/8, but later examples were computed half a stop faster, to f/6.8.[24] Several prototype examples of Sphaerogon lenses were recovered as part of the Zeiss Lens Collection seized by the Army Signal Corps as war reparations in 1945;[25] the collection, which the Zeiss firm had retained as a record of their designs, was later documented by Mert, the former head of optical computation for CZJ, working under Signal Corps officer Edward Kaprelian.[26][27]

After the war, the Fisheye-Nikkor lens was mated to a medium format camera and was produced in slightly modified form (focal length increased slightly to 16.3 mm) as the "Sky-image Recording Camera" in March 1957 for the Japanese government,[28] followed by a commercial release as the Nikon Fisheye Camera (also known as the "Nikon Sky Camera" or "Nikon Cloud Camera") in September 1960, which had a retail price of 200,000 (equivalent to 1,130,000 in 2019).[29] The revised lens created a circular image 50 mm (2.0 in) in diameter and covered a complete hemispherical field of 180.[30] Only 30 examples of the Nikon Fisheye Camera were manufactured, and of those, 18 were sold to customers, mainly in the United States; Nikon likely destroyed the remaining stock to avoid tax penalties.[31] Photographs taken with the Fisheye Camera that were published in Life in 1957 marked the first wide exposure of the public to fisheye distortion;[32] including a photograph of the United States Senate caucus room, taken by Ed Clark and published in an April 1957 issue,[33] and a photograph of pole vaulter Bob Gutowski taken by Ralph Crane, published in July 1957.[34]

The Nikon Fisheye Camera was discontinued in September 1961,[28] and Nikon subsequently introduced the first regular production fisheye lens for 35 mm cameras in 1962,[12] the Fisheye-Nikkor 8 mm f/8,[35] which required the reflex mirror on its Nikon F and Nikkormat cameras to be locked up prior to mounting the lens. Prior to the early 1960s, fisheye lenses were used primarily by professional and scientific photographers, but the advent of the fisheye for the 35 mm format increased its popular use.[36] The Fisheye-Nikkor 8 mm f/8 has a field of view of 180 and uses 9 elements in 5 groups; it has a fixed focus and built-in filters intended for black-and-white photography. Research indicates that fewer than 1,400 lenses were built.[37] As fisheye lenses became more widely available, the distinctive distortion grew in popularity, especially for album covers. For example, British fashion photographer Tim Walker used a fisheye lens to capture the cover of Harry Styles' 2019 pop/rock album, Fine Line.[38] Other genres that have taken advantage of the fisheye lens look include punk rock, hip-hop, and skateboarding videos.[32]

Contemporaneously, other Japanese manufacturers were developing the so-called "full-frame" or diagonal fisheyes, which captured approximately a 180 field of view across the diagonal of the film frame. The first such diagonal fisheye was the Fish-eye Takumar 18 mm f/11, released by Pentax (Asahi Optical) in 1962,[41][42][43] followed by the slightly faster UW Rokkor-PG 18 mm f/9.5 from Minolta in 1966.[44] Both of these were reflex-viewing and fixed-focus. Both Pentax and Minolta followed up with faster lenses with variable focus in 1967 (Super Fish-eye-Takumar 17 mm f/4)[45] and 1969 (Rokkor-OK 16 mm f/2.8),[46][47] respectively. The 16 mm Rokkor was later adopted by Leica as the Fisheye-Elmarit-R (1974) for its SLRs and then converted to autofocus (1986) for the Alpha system. As of 2018[update], the same basic optical design is still sold as the Sony SAL16F28.

Unlike rectilinear lenses, fisheye lenses are not fully characterised by focal length and aperture alone. Angle of view, image diameter, projection type, and sensor coverage all vary independently of these.

In a circular fisheye lens, the image circle is inscribed in the film or sensor area; in a diagonal ("full-frame") fisheye lens, the image circle is circumscribed around the film or sensor area. This implies that using a fisheye lens for a different format than it was intended for is easy (as opposed to a rectilinear lens), and may change its characteristic.

Further, different fisheye lenses map ("distort") images differently, and the manner of distortion is referred to as their mapping function. A common type for consumer use is equisolid angle.

For APS and m43 cameras, several lenses have emerged that retain a 180 field of view on a crop body. The first of these was the Sigma 4.5 mm.[49] Sunex also makes a 5.6 mm fisheye lens that captures a circular 185 field of view on a 1.5x Nikon and 1.6x Canon DSLR cameras.

More recently, the Japanese manufacturer Entaniya offers several fisheye lenses with angles of view up to 250 on 35 mm full frame, and up to 280 on smaller sensors (see list below). In 2018, Venus Optics introduced a 210 fisheye lens for the Micro Four Thirds system.[53]

The 8 mm and 7.5 mm circular fisheye lenses made by Nikon have proven useful for scientific purposes because of their equidistant (equiangular) projection, in which distance along the radius of the circular image is proportional to the zenith angle.

As fisheye lenses gained popularity in general photography, camera companies began manufacturing fisheye lenses with an enlarged image circle to cover the entire rectangular film frame. They are called diagonal, or sometimes "rectangular" or "full-frame", fisheyes. (This was well before digital photography, so the use of the term "full frame" with respect to fisheyes has nothing to do with the use of the term to designate a digital sensor measuring 36x24 mm).[54]

The angle of view produced by diagonal fisheyes only measures 180 from corner to corner: they have a 180 diagonal angle of view (AOV), while the horizontal and vertical angles of view will be smaller. For an equisolid angle 15 mm full-frame fisheye, the horizontal AOV will be 147, and the vertical AOV will be 94.[55]

To obtain the same effect on digital cameras with smaller sensors, shorter focal lengths are required. Nikon makes a 10.5 mm fisheye for their APS DX SLRs.[56] Several other companies make "full frame", i.e. diagonal, fisheyes for APS and m43 cameras, see next paragraph. e24fc04721