# 25. Why do objects look distorted when photographed with a wide angle lens?

## Description

This article is from the
Photographic Lenses FAQ, by David Jacobson with numerous
contributions by others.

# 25. Why do objects look distorted when photographed with a wide angle lens?

This is because the size of the image of an object depends on the
distance the object is from the lens. This is not a defect in the
lens---even pinhole cameras with no lens at all exhibit this
perspective effect.

For image calculation purposes, think of the lens as being a pinhole
one focal length in front of the film, and centered over the center of
the film. (If the lens is not focussed at infinity, the distance from
the film will be somewhat larger.) Then the image of an object point
can be found by drawing a straight line from the object point through
the pinhole and finding its intersection with the film. That line
represents one light ray. (Diffraction and out-of-focus conditions
have been ignored here, since they are irrelevant to this effect.)

If you do this, you'll find that the image of a nearby object will be
larger than the image of the same object farther away, by the ratio of
the distances. You'll also find that any straight line in object
space, no matter at what angle or position, will be rendered as a
straight line on the film. (Proof outline: a line, and a point not on
the line define a plane. All rays from the object line will stay in
the plane defined by the line and the pinhole, and the intersection of
that plane with the film plane is a straight line.) But parallel
lines in object space are not necessarily parallel on the film.

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