Editing Perspective distortion (section)

== Influencing factors ==

Perspective distortion is influenced by the relationship between two factors: the [[angle of view]] at which the image is captured by the [[camera]] and the angle of view at which the photograph of the subject is presented or viewed.

=== Angle of view of the capture ===

When photographs are viewed ''at the ordinary viewing distance'', the angle of view at which the image is captured accounts completely for the appearance of perspective distortion. The general assumption that "undoctored" photos cannot distort a scene is incorrect. Perspective distortion is particularly noticeable in [[portrait]]s taken with wide-angle lenses at short camera-to-subject distances.  They generally give an unpleasant impression, making the nose appear too large with respect to the rest of the face, and distorting the facial expression. Framing the same subject identically while using a moderate telephoto or long focus lens (with a narrow angle of view) flattens the image to a more flattering perspective. It is for this reason that, for a 35&nbsp;mm camera, lenses with focal lengths from about 85 through 135&nbsp;mm are generally considered to be good portrait lenses. It does however make difference, whether the photograph is taken landscape or portrait. A 50&nbsp;mm lens is suitable for photographing people when the orientation is landscape. Conversely, using lenses with much longer focal lengths for portraits results in more extreme flattening of facial features, which also may be objectionable to the viewer.<ref name="PSA Journal 2008">{{cite web |date=2008-05-06 |title=Best viewing distance for photographers - determining at what distance a photograph should be viewed - PSA Journal - Find Articles at BNET |url=https://www.findarticles.com/p/articles/mi_m1306/is_n9_v56/ai_8851922 |url-status=dead |archive-url=https://web.archive.org/web/20100723160516/https://www.findarticles.com/p/articles/mi_m1306/is_n9_v56/ai_8851922 |archive-date=2010-07-23 |access-date=2023-06-04 |publisher=PSA Journal}}</ref>

=== Photograph viewing distance ===

Photographs are ordinarily viewed at a distance approximately equal to their diagonal{{Citation needed|date=May 2011}}. When viewed at this distance, the distortion effects created by the angle of view of the capture are apparent. However, theoretically, if one views pictures exhibiting extension (wide angle) distortion at a closer distance, thus widening the angle of view of the presentation, then the phenomenon abates.  Similarly, viewing pictures exhibiting compression (telephoto) distortion from a greater distance, thus narrowing the angle of view of the presentation, reduces the effect. In both cases, at some critical distance, the apparent distortion disappears completely.

=== Examples ===

Below, a series of three photos shows the same scene shot from the same position with three different lenses: a wide-angle lens, a normal lens, and a telephoto lens. Notice that because the proportions in the image do not change with the angle of view, if the photos made with the wide-angle lens and the normal lens were cropped to contain the same scene as the photo made with the telephoto lens, then the image content would be exactly the same. The apparent difference in proportions results solely from the content added around the edges of the frame in the normal lens photo and the wide-angle photo.

<gallery mode="packed" heights="195" 
 caption="Photos taken using a [[135 film|35 mm]] still camera at a constant distance from the subject with a 28&nbsp;mm lens, a 50&nbsp;mm lens and a 70&nbsp;mm lens.''>
File:Angleofview 28mm f4.jpg|28 mm
File:Angleofview 50mm f4.jpg|50 mm
File:Angleofview 70mm f4.jpg|70 mm
</gallery>

{{clear}}

Below, a series of four photos shows an object framed as nearly the same as possible with four different lenses. As a result of the different [[angle of view]] of each lens, the photographer moved closer to the object with each photo. Note that the angle of view changes significantly (compare the background in each photo), and the distance between objects appears greater with each succeeding image. In the fourth image at the lower right, taken with the widest lens, the building behind the object appears much further away than in reality.

<gallery mode="packed" heights="150" caption="Photos taken using a 35&amp;nbsp;mm camera with a 100&amp;nbsp;mm, a 70&amp;nbsp;mm, a 50&amp;nbsp;mm, and a 28&amp;nbsp;mm lens, at different distances from the subject.">
File:Sameframe 100mm f8.jpg|100mm
File:Sameframe 70mm f8.jpg|70 mm
File:Sameframe 50mm f8.jpg|50 mm
File:Sameframe 28mm f8.jpg|28 mm
</gallery>