In photography and cinematography, perspective distortion is a warping or transformation of objects and surrounding areas that differ significantly from objects that would look like with normal focal lengths, due to the relative nearest scale and distant features. The perspective distortion is determined by the relative distance at which the image is captured and viewed, and since the image angle (as captured) becomes wider or narrower than the point of view in which the image is viewed, the relative distances are distinctly different from expected. Associated with this concept is axial enlargement - the perceived depth of the object at a certain magnification.
The perspective distortion takes two forms: extension distortion and compression distortion, also called wide-angle distortion and long lens or < i> telephoto distortion, when talking about images with the same field size. Extension or wide angle distortion can be seen in close-up images using wide-angle lens (with a wider viewing angle than normal lens ). The objects close to the lens appear very large relative to the more distant objects, and the distant objects appear abnormally small and thus further - the distance is extended. Long telephoto compression, lens, or distortion can be seen in images taken remotely using longer focus lenses or more common telephoto subtypes (with a narrower view angle than normal lens ). Far objects look more or less the same - the closer objects are small, and the more distant objects are so large that the viewer can not see the relative distance between distant objects - compressed distances.
Note that linear perspective changes are caused by distance, not by lens per se - two portraits of the same scene from the same distance will show identical perspective geometry, regardless of the lens used. However, since the wide-angle lens has a wider field of view, they are generally used up close, while telephoto lenses have a narrower field of view and are generally used from further distances. For example, if standing in the distance so that a normal lens captures a person's face, a shot with a wide-angle lens or telephoto lens from the same distance would have the exact same linear perspective geometry on the face, even though the wide-angle lens might fit the whole body into the shot, the telephoto lens only catches the nose. However, the harvest of these three images with the same coverage will produce the same perspective distortion - the nose will look the same in all three. Conversely, if all three lenses are used from a distance such that the face fills the field, the wide angle will be used closer, making the nose larger than the rest of the photo, and telephoto will be used further, making the nose smaller than the rest of the photo.
Beyond photography, extension distortions are familiar to many people through the rearview mirror (see "objects in the mirror closer than they look") and the peephole, although this often uses a fish eye lens, shows different distortions. The distortion of compression is best known in searching through binoculars or telescopes, as in telescopic shots, while similar effects are seen in fixed-strip photography, especially photo completion, where all arrests are parallel to the capture, eliminating the full perspective (sighting side).
Video Perspective distortion (photography)
Optics
Pertimbangkan sistem optik Gaussian yang ideal. Untuk sebagian besar tujuan, kita dapat mengasumsikan ruang gambar dan ruang objek berada dalam medium yang sama. Jadi, untuk objek dalam fokus, jarak antara lensa dan bidang gambar , jarak antara lensa dan objek , dan panjang fokus terkait oleh:
Pembesaran transversal terkait oleh
pembesaran aksial dari sebuah objek pada adalah laju perubahan jarak lensa-gambar sebagai jarak objek lensa perubahan. Untuk objek denotes kedalaman terbatas, seseorang dapat memahami pembesaran aksial rata-rata sebagai rasio kedalaman gambar dan kedalaman objek:
One can see that if the magnification remains constant, longer focal lengths result in smaller axial enlargements, and smaller focal lengths of larger axial enlargements. That is, when using a longer focal length when moving the camera/lens away from the object to maintain the same M magnification, the object looks more shallow, and the axial distance between objects seems shorter. The reverse - an increase in axial magnification - occurs with a shorter focal length when moving the camera/lens to the object.
Maps Perspective distortion (photography)
Influencing factor
The perspective distortion is influenced by the relationship between two factors: the point of view in which the image is captured by the camera and the point of view in which the subject photo is presented or viewed.
Capture View
When a photo is viewed in the usual viewing distance , the viewing angle in which the image is taken is completely for perspective distortion view. The general assumption that "unlisted" photos can not distort a scene is incorrect. The perspective distortion is highly visible in portraits taken with a wide-angle lens at a short camera-to-subject distance. They generally give an unpleasant impression, make the nose look too big on the whole face, and damage the facial expression. Same identical subject framing while using a medium-sized telephoto or long focus lens (with a narrow angle of view) equates the image to a more flattering perspective. For this reason, for 35 mm cameras, the lens with a focal length of about 85 to 135 mm is generally considered a good portrait lens. But it makes a difference, whether the photo was taken landscape or portrait. 50 mm lens is suitable for photographing people during landscape orientation. Instead, use a longer focal length lens for portraits on more extreme facial features, which may also be unpleasant for viewers.
Display distance of photo
Photographs are usually seen at more or less the same distance as their diagonal. When viewed at this distance, the distortion effects created by the viewing angle are clear. However, theoretically, if one looks at an image showing extension (wide angle) of distortion at closer distances, thus expanding the presentation angle, then the phenomenon subsides. Similarly, looking at images that show distortion (telephoto) compression from further distances, thus narrowing the presentation angle, reducing the effect. In both cases, at some critical distance, real distortion is completely lost.
Example
Below, a series of three photos show the same shooting scene from the same position with three different lenses: normal lens, wide-angle lens, and telephoto lens. Note that since the proportions in the image do not change with the viewing angle, if the photo is made with a wide-angle lens and the normal lens is trimmed to load the same scene as a photo made with telephoto lenses, the image content will be exactly the same. The real difference in proportion is only generated from the added content around the edges of the frame in normal lens photos and wide-angle photos.
Below, a series of four photographs show objects that are framed as nearly as possible with four different lenses. As a result of different viewpoints of each lens, the photographer moves closer to the object with each photo. Note that the viewing angle changes significantly (compare the background in each photo), and the distance between objects appears larger with each subsequent image. In the fourth image at the bottom right, taken with the widest lens, the building behind the object looks much further than in reality.
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Photos taken using a 35 mm camera with a lens of 100 mm, 70 mm, 50 mm, and 28 mm, at different distances from the subject.
Artistic use
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Although perspective distortions are often annoying when not intentional, it is also intentionally used for artistic purposes. The expansion (wide angle) distortion is often applied to emphasize some elements of the scene by making it appear larger and spatially removed from other elements. Distortion compression (telephoto) is often used to provide the appearance of compressed distances between distant objects, such as buildings or cars to convey a feeling of congestion. Longer lenses magnify the subject more, seem to compress the distance and (when focused on the foreground) blur the background due to the shallower depth of the field. Larger lens tends to increase the distance between objects while allowing greater depth of field.
Another result of using a wide-angle lens is a more noticeable perspective distortion when the camera is not aligned perpendicular to the subject: parallel lines meet at the same level as with normal lenses, but are assembled more due to the larger total area. For example, buildings seem to fall backwards are much more severe when the camera is pointing up from the ground surface than if photographed with a normal lens at the same distance from the subject, as more subject buildings are seen in angular shots.
Because different lenses generally require different camera subject distances to maintain the size of the subject, changing the viewing angle can indirectly change perspective, change the relative size of the subject and background clearly. If identical field sizes are maintained, the wide-angle lens makes the subject appear larger by introducing size differences along with the above-mentioned convergent lines, and they make the space and space around the subject appear wider by increasing the distance between the subject and the background (expanded perspective ).
Known mood and usage effect
The mood effect of the perspective distortion achieved by the extreme rectilinear wide-angle lens is that the resulting image looks odd and uncomfortable, while not looking unrealistic like a curved fisheye lens that displays barrel distortion. The effect is especially noticeably closer to the subject, as the number increases the shorter the focal length on the same field size.
One of the most famous directors who often use a wide-angle rectangular lens to achieve the distinctive marking style defined by extreme perspective distortion is Terry Gilliam. Also Stanley Kubrick (in Paths of Glory, and Dr Strangelove, among others) and Orson Welles (in The Trial), some of it Orson Welles' London , segment Four Club Members ), Sam Peckinpah (in Straw Dog ), and Sidney Lumet (in The Offense > i>) sometimes do the same in the past, though mostly in moderation, for a single shot or sequence only, while Gilliam hardly ever uses a lens longer than 14mm, which has collected lenses of a certain focal length informal nickname "The Gilliam" among the filmmakers. Jean-Pierre Jeunet and Marc Caro, two French filmmakers influenced by Gilliam, adopted their distinctive wide-angle photography in two of their "Gilliamesque" features, Cake Shops and Children's Cities Missing me. Orson Welles's The Trial is well-known for profoundly influencing Gilliam's signature style years before the former American patriarch joined the Monty Python comedy troupe while only becoming a one-feature style for Welles.
Due to the peculiar and peculiar mood effect typical of wide-angle lenses, films that use such perspective distortions can often be placed in one of two categories: Groteque and surrealist and fantasy satire, also to some extent black comedy (Gilliam, Jeunet & amp; Caro, Orson Welles, Strangelove ) on the one hand, and serious, more realistic films with certain advantages for social criticism on the other, while social conventions, collective societies, and/or the motives and actions of leaders are described as strange and absurd, and often also display tyrannical characters with conformist values ​​acting in a very hostile and prejudiced manner toward individualism and outsiders ( Paths of Glory , Straw Dog , The Offense ).
At the other end of the focal length specter, Leni Riefenstahl uses an extreme telephoto lens to compress a large crowd on Triumph of the Will while Adolf Hitler is viewed through normal and often low-angle lenses. to appear high in comparison.
In cinematography, perspective distortion also has a special effect in a camera known as zoom dolly, where the zoom lens zooms in at the same time as the camera moves toward the subject, in such a way as to keep the subject of the same size in the frame while the background "resizes" relative to the subject. This effect is made popular in movies Vertigo and Jaws . Another example of this can be seen in the first film of the Lord of the Rings, just before the Black Riders took to the streets. The dolly zoom is used to create a compression effect on the road.
Example
The photo below the gondola is an illustration of the use of extension distortion, and the photo of the building below is an example of compression distortion.
See also
- Foreshortening
- Control Perspective Lens (PC)
- Gradient texture
- Curvilinear Perspective
Note
External links
- Compresses distance and changes perspective
Source of the article : Wikipedia
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