A means of producing a three-dimensional image onto a two-dimensional surface by the use of lines, mainily by using real world parallel lines and making them converge in the plane of the photograph.

Converging parallel lines that move away from us appear to converge at the horizon. Sides of roads and the rails of railroads seem to merge together at extreme distance. This is an aspect of the relative size effect. Even though the sides of the roads or the rails are at a fixed distance they will appear smaller and smaller as they get further away from us.

When you zoom with a lens but keep the distance from the lens to the subject the same, there will be no change in the perspective. The zooming will only change the size of the subjects in the frame.

By using the right combination of distance to the subject as well as the lens focal length, a photographer can create an image that looks deep or shallow. The feeling of depth or shallowness is only an illusion, but it is a very important compositional factor.