El ángulo de visión es la variable decisiva para la percepción visual del tamaño o proyección del tamaño de un objeto.
![Ángulo de visión 2.png](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/0/08/Angle_of_view_2.png/220px-Angle_of_view_2.png)
Ángulo de visión y percepción del tamaño.
![Angle of view 1.png](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/5/5c/Angle_of_view_1.png/220px-Angle_of_view_1.png)
El tamaño percibido de un objeto depende del tamaño de la imagen proyectada en la retina . El tamaño de la imagen depende del ángulo de visión. Un objeto cercano y otro lejano pueden parecer del mismo tamaño si sus bordes producen el mismo ángulo de visión. Con un dispositivo óptico como gafas o binoculares , microscopio y telescopio se puede ampliar el ángulo de visión para que el objeto parezca más grande, lo que favorece el poder de resolución del ojo (ver ángulo visual ) [1] [2]
Ángulo de visión en fotografía
![](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/7/72/Angle_of_view.svg/260px-Angle_of_view.svg.png)
En fotografía , el ángulo de visión ( AOV ) [3] describe la extensión angular de una escena dada que es fotografiada por una cámara . Se usa indistintamente con el término campo de visión más general .
Es importante distinguir el ángulo de visión del ángulo de cobertura , que describe el rango de ángulos que una lente puede captar. Normalmente, el círculo de imagen producido por una lente es lo suficientemente grande como para cubrir la película o el sensor por completo, posiblemente incluyendo algunas viñetas hacia el borde. Si el ángulo de cobertura de la lente no llena el sensor, el círculo de la imagen será visible, normalmente con un fuerte viñeteado hacia el borde, y el ángulo de visión efectivo se limitará al ángulo de cobertura.
![](http://wikiimg.tojsiabtv.com/wikipedia/en/thumb/5/54/Angle_of_View_F_V_Chambers_1916.png/360px-Angle_of_View_F_V_Chambers_1916.png)
![](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/d/d3/Camera_focal_length_distance_house_animation.gif/220px-Camera_focal_length_distance_house_animation.gif)
El ángulo de visión de una cámara depende no solo del objetivo, sino también del sensor. Los sensores digitales suelen ser más pequeños que una película de 35 mm , y esto hace que la lente tenga un ángulo de visión más estrecho que con una película de 35 mm, por un factor constante para cada sensor (llamado factor de recorte ). En las cámaras digitales cotidianas, el factor de recorte puede oscilar entre 1 ( SLR digitales profesionales ), 1,6 (SLR de consumo), 2 ( Micro Four Thirds ILC) y 6 (la mayoría de las cámaras compactas ). Por lo tanto, una lente estándar de 50 mm para fotografía de 35 mm actúa como una lente de "película" estándar de 50 mm en una SLR digital profesional, pero actuaría más cerca de una lente de 80 mm (1,6 x 50 mm) en muchas DSLR del mercado medio, y la de 40 El ángulo de visión de grados de una lente estándar de 50 mm en una cámara de película es equivalente a una lente de 80 mm en muchas SLR digitales.
Calcular el ángulo de visión de una cámara
Para lentes que proyectan imágenes rectilíneas (no distorsionadas espacialmente) de objetos distantes, la distancia focal efectiva y las dimensiones del formato de imagen definen completamente el ángulo de visión. Los cálculos para lentes que producen imágenes no rectilíneas son mucho más complejos y, al final, no son muy útiles en la mayoría de las aplicaciones prácticas. (En el caso de una lente con distorsión, por ejemplo, una lente de ojo de pez , una lente más larga con distorsión puede tener un ángulo de visión más amplio que una lente más corta con baja distorsión) [5] El ángulo de visión puede medirse horizontalmente (desde la izquierda al borde derecho del marco), verticalmente (desde la parte superior a la inferior del marco) o diagonalmente (desde una esquina del marco hasta su esquina opuesta).
Para una lente que proyecta una imagen rectilínea (enfocada al infinito, ver derivación ), el ángulo de visión ( α ) se puede calcular a partir de la dimensión elegida ( d ) y la distancia focal efectiva ( f ) de la siguiente manera: [6]
representa el tamaño de la película (o sensor) en la dirección medida (ver más abajo: efectos del sensor ) . Por ejemplo, para una película de 35 mm que tiene 36 mm de ancho y 24 mm de alto, mm se utilizaría para obtener el ángulo de visión horizontal y mm para el ángulo vertical.
Debido a que esta es una función trigonométrica, el ángulo de visión no varía de manera bastante lineal con el recíproco de la distancia focal. Sin embargo, a excepción de las lentes gran angular, es razonable aproximar radianes o degrees.
The effective focal length is nearly equal to the stated focal length of the lens (F), except in macro photography where the lens-to-object distance is comparable to the focal length. In this case, the magnification factor (m) must be taken into account:
(In photography is usually defined to be positive, despite the inverted image.) For example, with a magnification ratio of 1:2, we find and thus the angle of view is reduced by 33% compared to focusing on a distant object with the same lens.
Angle of view can also be determined using FOV tables or paper or software lens calculators.[7]
![](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/3/3e/Camera_focal_length_vs_crop_factor_vs_angle_of_view.svg/600px-Camera_focal_length_vs_crop_factor_vs_angle_of_view.svg.png)
Example
Consider a 50 mm camera with a lens having a focal length of F = 50 mm. The dimensions of the 35 mm image format are 24 mm (vertically) × 36 mm (horizontal), giving a diagonal of about 43.3 mm.
At infinity focus, f = F, the angles of view are:
- horizontally,
- vertically,
- diagonally,
Derivation of the angle-of-view formula
Consider a rectilinear lens in a camera used to photograph an object at a distance , and forming an image that just barely fits in the dimension, , of the frame (the film or image sensor). Treat the lens as if it were a pinhole at distance from the image plane (technically, the center of perspective of a rectilinear lens is at the center of its entrance pupil):[8]
![Lens angle of view.svg](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/0/0c/Lens_angle_of_view.svg/535px-Lens_angle_of_view.svg.png)
Now is the angle between the optical axis of the lens and the ray joining its optical center to the edge of the film. Here is defined to be the angle-of-view, since it is the angle enclosing the largest object whose image can fit on the film. We want to find the relationship between:
- the angle
- the "opposite" side of the right triangle, (half the film-format dimension)
- the "adjacent" side, (distance from the lens to the image plane)
Using basic trigonometry, we find:
which we can solve for α, giving:
To project a sharp image of distant objects, needs to be equal to the focal length, , which is attained by setting the lens for infinity focus. Then the angle of view is given by:
- where
Note that the angle of view varies slightly when the focus is not at infinity (See breathing (lens)), given by rearranging the lens equation.
Macro photography
For macro photography, we cannot neglect the difference between and . From the thin lens formula,
- .
From the definition of magnification, , we can substitute and with some algebra find:
Defining as the "effective focal length", we get the formula presented above:
- where .
A second effect which comes into play in macro photography is lens asymmetry (an asymmetric lens is a lens where the aperture appears to have different dimensions when viewed from the front and from the back). The lens asymmetry causes an offset between the nodal plane and pupil positions. The effect can be quantified using the ratio (P) between apparent exit pupil diameter and entrance pupil diameter. The full formula for angle of view now becomes:[9]
Medir el campo de visión de una cámara
![](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/d/d6/FOV_test_Optics_apparatus.svg/300px-FOV_test_Optics_apparatus.svg.png)
In the optical instrumentation industry the term field of view (FOV) is most often used, though the measurements are still expressed as angles.[10] Optical tests are commonly used for measuring the FOV of UV, visible, and infrared (wavelengths about 0.1–20 μm in the electromagnetic spectrum) sensors and cameras.
The purpose of this test is to measure the horizontal and vertical FOV of a lens and sensor used in an imaging system, when the lens focal length or sensor size is not known (that is, when the calculation above is not immediately applicable). Although this is one typical method that the optics industry uses to measure the FOV, there exist many other possible methods.
UV/visible light from an integrating sphere (and/or other source such as a black body) is focused onto a square test target at the focal plane of a collimator (the mirrors in the diagram), such that a virtual image of the test target will be seen infinitely far away by the camera under test. The camera under test senses a real image of the virtual image of the target, and the sensed image is displayed on a monitor.[11]
![](http://wikiimg.tojsiabtv.com/wikipedia/commons/thumb/e/ec/FOV_Target_on_Monitor.svg/250px-FOV_Target_on_Monitor.svg.png)
The sensed image, which includes the target, is displayed on a monitor, where it can be measured. Dimensions of the full image display and of the portion of the image that is the target are determined by inspection (measurements are typically in pixels, but can just as well be inches or cm).
- = dimension of full image
- = dimension of image of target
The collimator's distant virtual image of the target subtends a certain angle, referred to as the angular extent of the target, that depends on the collimator focal length and the target size. Assuming the sensed image includes the whole target, the angle seen by the camera, its FOV, is this angular extent of the target times the ratio of full image size to target image size.[12]
The target's angular extent is:
- where is the dimension of the target and is the focal length of collimator.
The total field of view is then approximately:
or more precisely, if the imaging system is rectilinear:
This calculation could be a horizontal or a vertical FOV, depending on how the target and image are measured.
Tipos de lentes y efectos
Focal length
Lenses are often referred to by terms that express their angle of view:
- Fisheye lenses, typical focal lengths are between 8 mm and 10 mm for circular images, and 15–16 mm for full-frame images. Up to 180° and beyond.
- A circular fisheye lens (as opposed to a full-frame fisheye) is an example of a lens where the angle of coverage is less than the angle of view. The image projected onto the film is circular because the diameter of the image projected is narrower than that needed to cover the widest portion of the film.
- Ultra wide angle lens is a rectilinear which is less than 24 mm of focal length in 35 mm film format, here 14 mm gives 114° and 24 mm gives 84° .
- Wide-angle lenses (24–35 mm in 35 mm film format) cover between 84° and 64°
- Normal, or Standard lenses (36–60 mm in 35 mm film format) cover between 62° and 40°
- Long focus lenses (any lens with a focal length greater than the diagonal of the film or sensor used)[13] generally have an angle of view of 35° or less.[14] Since photographers usually only encounter the telephoto lens sub-type,[15] they are referred to in common photographic parlance as:
- "Medium telephoto", a focal length of 85 mm to 250 mm in 35 mm film format covering between 30° and 10°[16]
- "Super telephoto" (over 300 mm in 35 mm film format) generally cover between 8° through less than 1°[16]
Zoom lenses are a special case wherein the focal length, and hence angle of view, of the lens can be altered mechanically without removing the lens from the camera.
Characteristics
For a given camera–subject distance, longer lenses magnify the subject more. For a given subject magnification (and thus different camera–subject distances), longer lenses appear to compress distance; wider lenses appear to expand the distance between objects.
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 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 can indirectly distort perspective, changing the apparent relative size of the subject and foreground.
If the subject image size remains the same, then at any given aperture all lenses, wide angle and long lenses, will give the same depth of field.[17]
Examples
An example of how lens choice affects angle of view.
![]() 28 mm lens, 65.5° × 46.4° | ![]() 50 mm lens, 39.6° × 27.0° |
![]() 70 mm lens, 28.9° × 19.5° | ![]() 210 mm lens, 9.8° × 6.5° |
Ángulos de visión comunes de la lente
This table shows the diagonal, horizontal, and vertical angles of view, in degrees, for lenses producing rectilinear images, when used with 36 mm × 24 mm format (that is, 135 film or full-frame 35 mm digital using width 36 mm, height 24 mm, and diagonal 43.3 mm for d in the formula above).[18] Digital compact cameras sometimes state the focal lengths of their lenses in 35 mm equivalents, which can be used in this table.
For comparison, the human visual system perceives an angle of view of about 140° by 80°.[19]
Focal length (mm) | Diagonal (°) | Vertical (°) | Horizontal (°) |
---|---|---|---|
0 | 180.0 | 180.0 | 180.0 |
2 | 169.4 | 161.1 | 166.9 |
12 | 122.0 | 90.0 | 111.1 |
14 | 114.2 | 81.2 | 102.7 |
16 | 107.1 | 73.9 | 95.1 |
20 | 94.5 | 61.9 | 82.4 |
24 | 84.1 | 53.1 | 73.7 |
35 | 63.4 | 37.8 | 54.4 |
50 | 46.8 | 27.0 | 39.6 |
70 | 34.4 | 19.5 | 28.8 |
85 | 28.6 | 16.1 | 23.9 |
105 | 23.3 | 13.0 | 19.5 |
200 | 12.3 | 6.87 | 10.3 |
300 | 8.25 | 4.58 | 6.87 |
400 | 6.19 | 3.44 | 5.15 |
500 | 4.96 | 2.75 | 4.12 |
600 | 4.13 | 2.29 | 3.44 |
700 | 3.54 | 1.96 | 2.95 |
800 | 3.10 | 1.72 | 2.58 |
1200 | 2.07 | 1.15 | 1.72 |
Efectos del tamaño del sensor ("factor de recorte")
As noted above, a camera's angle of view depends not only on the lens, but also on the sensor used. Digital sensors are usually smaller than 35 mm film, causing the lens to usually behave as a longer focal length lens would behave, and have a narrower angle of view than with 35 mm film, by a constant factor for each sensor (called the crop factor). In everyday digital cameras, the crop factor can range from around 1 (professional digital SLRs), to 1.6 (mid-market SLRs), to around 3 to 6 for compact cameras. So a standard 50 mm lens for 35 mm photography acts like a 50 mm standard "film" lens even on a professional digital SLR, but would act closer to a 75mm (1.5×50 mm Nikon) or 80mm lens (1.6×50 mm Canon) on many mid-market DSLRs, and the 40 degree angle of view of a standard 50mm lens on a film camera is equivalent to a 28–35 mm lens on many digital SLRs.
The table below shows the horizontal, vertical and diagonal angles of view, in degrees, when used with 22.2 mm × 14.8 mm format (that is Canon's DSLR APS-C frame size) and a diagonal of 26.7 mm.
Focal length (mm) | Diagonal (°) | Vertical (°) | Horizontal (°) |
---|---|---|---|
2 | 162.9 | 149.8 | 159.6 |
4 | 146.6 | 123.2 | 140.4 |
7 | 124.6 | 93.2 | 115.5 |
9 | 112.0 | 78.9 | 101.9 |
12 | 96.1 | 63.3 | 85.5 |
14 | 87.2 | 55.7 | 76.8 |
16 | 79.6 | 49.6 | 69.5 |
17 | 76.2 | 47.0 | 66.3 |
18 | 73.1 | 44.7 | 63.3 |
20 | 67.4 | 40.6 | 58.1 |
24 | 58.1 | 34.3 | 49.6 |
35 | 41.7 | 23.9 | 35.2 |
50 | 29.9 | 16.8 | 25.0 |
70 | 21.6 | 12.1 | 18.0 |
85 | 17.8 | 10.0 | 14.9 |
105 | 14.5 | 8.1 | 12.1 |
200 | 7.6 | 4.2 | 6.4 |
210 | 7.3 | 4.0 | 6.1 |
300 | 5.1 | 2.8 | 4.2 |
400 | 3.8 | 2.1 | 3.2 |
500 | 3.1 | 1.7 | 2.5 |
600 | 2.5 | 1.4 | 2.1 |
700 | 2.2 | 1.2 | 1.8 |
800 | 1.9 | 1.1 | 1.6 |
Cinematografía y videojuegos
Ratio | 1080p resolution | Common name | Video format / lens |
---|---|---|---|
32:27 | 1280x1080p | DVCPRO HD | |
4:3 | 1440x1080p | ||
16:9 | 1920x1080p | Widescreen | |
2:1 | 2160x1080 | 18:9 | Univisium |
64:27 | 2560x1080p | Ultra-Widescreen | Cinemascope / Anamorphic |
32:9 | 3840x1080p | Super Ultra-Widescreen | Ultra-Widescreen 3.6 / Anamorphic 3.6 |
Modifying the angle of view over time (known as zooming), is a frequently used cinematic technique, often combined with camera movement to produce a "dolly zoom" effect, made famous by the film Vertigo. Using a wide angle of view can exaggerate the camera's perceived speed, and is a common technique in tracking shots, phantom rides, and racing video games. See also Field of view in video games.
Ver también
- 35 mm equivalent focal length
- Camera angle
- Camera coverage
- Camera operator
- Cinematic techniques
- Field of view
- Filmmaking
- Multiple-camera setup
- Single-camera setup
- Video production
- Image sensor format
- Crop factor
- Ultrawide formats
notas y referencias
- ^ Light microscopy online theory and application - Optics page 24}}]
- ^ Georg Eisner: Perspektive und Visuelles System page 134]
- ^ Tim Dobbert (November 2012). Matchmoving: The Invisible Art of Camera Tracking, 2nd Edition. John Wiley & Sons. p. 116. ISBN 9781118529669.
- ^ Neil Wayne Northey (September 1916). Frank V. Chambers (ed.). "The Angle of View of your Lens". The Camera. Columbia Photographic Society. 20 (9).
- ^ "Canon EF 15mm f/2.8 Fisheye Lens Review". The-Digital-Picture.com. Archived from the original on 7 August 2017. Retrieved 1 May 2018.
- ^ Ernest McCollough (1893). "Photographic Topography". Industry: A Monthly Magazine Devoted to Science, Engineering and Mechanic Arts. Industrial Publishing Company, San Francisco: 399–406.
- ^ CCTV Field of View Camera Lens Calculations Archived 2008-08-22 at the Wayback Machine by JVSG, December, 2007
- ^ Kerr, Douglas A. (2008). "The Proper Pivot Point for Panoramic Photography" (PDF). The Pumpkin. Retrieved 2014-03-20.
- ^ Paul van Walree (2009). "Center of perspective". Archived from the original on 30 April 2009. Retrieved 24 January 2010.
- ^ Holst, G.C. (1998). Testing and Evaluation of Infrared Imaging Systems (2nd ed.). Florida:JCD Publishing, Washington:SPIE.
- ^ Mazzetta, J.A.; Scopatz, S.D. (2007). Automated Testing of Ultraviolet, Visible, and Infrared Sensors Using Shared Optics. Infrared Imaging Systems: Design Analysis, Modeling, and Testing XVIII,Vol. 6543, pp. 654313-1 654313-14
- ^ Electro Optical Industries, Inc.(2005). EO TestLab Methadology. In Education/Ref. "Archived copy". Archived from the original on 2008-08-28. Retrieved 2008-05-22.CS1 maint: archived copy as title (link).
- ^ Ray, Sidney F. (1 May 2018). Applied Photographic Optics: Lenses and Optical Systems for Photography, Film, Video, Electronic and Digital Imaging. Focal. ISBN 9780240515403. Retrieved 1 May 2018 – via Google Books.
- ^ Lynne Warren, Encyclopedia of 20th century photography, page 211
- ^ Langford, Michael (1 May 2018). Basic Photography. Focal Press. ISBN 9780240515922. Retrieved 1 May 2018 – via Google Books.
- ^ a b "Your Site". www.photographywebsite.co.uk. Retrieved 1 May 2018.
- ^ Reichmann, Michael. "Do Wide Angle Lenses Really Have Greater Depth of Field Than Telephotos?". Archived from the original on 2011-06-10. Retrieved 2011-07-08.
- ^ However, most interchangeable-lens digital cameras do not use 24×36 mm image sensors and therefore produce narrower angles of view than set out in the table. See crop factor and the subtopic digital camera issues in the article on wide-angle lenses for further discussion.
- ^ Kollin, Joel S. (1993). A Retinal Display for Virtual-Environment Applications. Proceedings of Society for Information Display. XXIV. p. 827. Archived from the original on 2013-07-04. Retrieved 2014-04-27.
- ^ The image examples uses a 5.1–15.3 mm lens which is called a 24 mm 3× zoom by the producer (Ricoh Caplio GX100 Archived 2009-06-01 at the Wayback Machine)
enlaces externos
- Simple Explanation of Angle of View and Focal Length
- Angle of View on digital SLR cameras with reduced sensor size
- Focal Length and Angle of View