Understand Perspective in Digital Photography

The image formed by a lens is as realistic as one perceived by our eyes, since vision and photography follow very similar rules. Nonetheless, to photographically reproduce a scene we don't need to know or apply the laws of perspective. It isn't necessary to how to race this or that line simply because the lens does it for us. The projection of three-dimensional space on the plane that a realistic painter is going to use has a structure of lines and escape points were the elements of the scene are placed. With a lens, this projection is automatic. Therefore, the photographers usually ignores the relation there is between the choice of a point of view or of a lens and the characteristics of the resulting image made precisely by the laws of perspective.

Space an Planes

The projection of a curved space on a plane can cause distortions, as we have seen in the case of extreme angulars (7.2.3.2). More generally, the fact that the surface of the film is flat causes that in a photograph the exit points are always more accented as long as the plane of the film isn't parallel to the

plane were they are produced. In the camera, a variation in the angle the direction of observation forms with any given plane causes a change in the inclination of all the exit points; on the other hand, in the interior of the eye, this change isn't as manifested because when changing the observation direction (when turning the eye or the head), the curvature of the retina counteracts the larger or smaller inclination of our line of vision regarding the observed plane.

For example; if we observe a tall building from the street, the vertical lines appear "almost" parallel because our retina is curved and we have a visual memory that helps us see it that way; when changing the observation direction (passing your look from the inferior part of the building to the superior), the aspect of the image doesn't vary notably. On the other hand, in a focal screen there are exit lines as long as the photographed plane and the plane of the film aren't parallel; in these conditions, a rectangular façade appears in the photograph with the shape of a trapeze; if we frame the lower part of the building and change the observation direction, we will see that also the inclination of the vertical lines varies visibly and in direct relation with the angle the lenses axis and the framed plane form.