Ultra wide angle lens
Encyclopedia
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
whose focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
is shorter than the short side of film or sensor.
Thus the term denotes a different range of lenses, relative to the size of the sensor in the camera in question.
- For APS-CAPS-CAdvanced Photo System type-C is an image sensor format approximately equivalent in size to the Advanced Photo System "classic" size negatives...
any lens shorter than 15 mm is considered ultra wide angle. - For 35 mm film or full-frame sensor any lens shorter than 24 mm
- For 6x45 any lens shorter than 41 mm
- For 6x6 and 6x7 any lens shorter than 56 mm
'Fisheye' and rectilinear lenses
Fisheye lens
In photography, a fisheye lens is a wide-angle lens that takes in a broad, panoramic and hemispherical image. Originally developed for use in meteorology to study cloud formation and called "whole-sky lenses", fisheye lenses quickly became popular in general photography for their unique, distorted...
es with curvilinear
Curvilinear perspective
Curvilinear perspective is a graphical projection used to draw 3D objects on 2D surfaces. It was formally codified in 1968 by the artists and art historians André Barre and Albert Flocon in the book La Perspective curviligne, which was translated into English in 1987 as Curvilinear Perspective:...
barrel distortion
Barrel distortion
In geometric optics and cathode ray tube displays, distortion is a deviation from rectilinear projection, a projection in which straight lines in a scene remain straight in an image...
, and rectilinear lens
Rectilinear lens
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 opposed to being curved. In other words, it is a lens with little or no barrel or pincushion distortion...
es which are designed so that straight lines in the scene will render straight (uncurved) in the photographic image and thus lack the extreme distortion that is characteristic of a fisheye lens. Neither denotes a particular range of focal lengths, the difference is only whether distortion is present or not. However, the shorter the focal length, the more difficult it is to implement rectilinear correction.
In fisheye lenses, the visual angle is close to or more than 180 degrees in at least one direction. For example, a “diagonal fish eye” would have a viewing angle of at least 180 degrees within the diagonals of the frame. A “Circular fisheye” would represent the image in the form of a circle.
Rectilinear ultra-wide angle lenses are used in photography and cinematography sometimes to achieve three-dimensional perspective distortion
Perspective distortion (photography)
In photography and cinematography, perspective distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features...
instead of simply two-dimensional barrel distortion. A notable, signature employment for this purpose is frequently seen in the films of Terry Gilliam
Terry Gilliam
Terrence Vance "Terry" Gilliam is an American-born British screenwriter, film director, animator, actor and member of the Monty Python comedy troupe. Gilliam is also known for directing several films, including Brazil , The Adventures of Baron Munchausen , The Fisher King , and 12 Monkeys...
, for instance.
Larger Depth of Field (DOF)
The DOF afforded by a ultra wide-angle lens is very great. Therefore the photographer has the ability to keep much or almost all of the scene in focus, with respect to the hyperfocal distance of the lens.Better Aperture Setting
Thanks to the small focal length, these lenses can shoot longer exposures without fear of camera shake in the image. (In longer lenses camera shake is multiplied by the zoom factor, but in shorter lenses it is much less apparent). This means that the photographer can afford to use a much smaller aperture if they choose, and still retain a balanced image.Undesirable Objects
With such a large visual angle, it can be very difficult at times to keep undesired objects such as light sources out of the image. However this does not always pose a problem, as even the sun in a photograph takes up such a small amount of space that its presence can often have little negative impact on the overall composition.Use of Filters
When using an ultra wide-angle lens, the sky often constitutes a very large portion of the frame, and may need to be darkened for the image to appear balanced. This is often achieved though the use of Polarizing or Gradient Filters.Development
The oldest "lenses", pinholes, keep perspective accurately. In images made from this technique, there is little or no distortion due to the rectilinear propagation of light. For a long time it was thought that only symmetrical optical diagrams could ensure the geometrically precise transfer of light without distortion becoming apparent near the edge of images (as the viewing angle increases). However, with modern technology and understanding of optics, super-wideangle objectives can these days eliminate distortion almost completely.Characteristics
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
. Wider lenses tend to magnify distance between objects while allowing greater depth of field.
Another result of using a wide-angle lens is a greater apparent perspective distortion
Perspective distortion (photography)
In photography and cinematography, perspective distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features...
when the camera is not aligned perpendicularly to the subject: parallel lines converge at the same rate as with a normal lens
Normal lens
In photography and cinematography a normal lens, also called a standard lens, is a lens that reproduces perspective that generally looks "natural" to a human observer under normal viewing conditions, as compared with lenses with longer or shorter focal lengths which produce an expanded or...
, but converge more due to the wider total field. For example, buildings appear to be falling backwards 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
Angle of view
In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view....
can indirectly distort
Perspective distortion (photography)
In photography and cinematography, perspective distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features...
perspective, changing the apparent relative size of the subject and foreground.
External links
- http://www.canon.com/camera-museum/camera/lens/ef/ultra_wide.html
- http://mamiya.co.uk/products.php?id=212
- http://mamiya.co.uk/products.php?id=198