In the world of photography, “perspective” refers to a visual effect that creates a sense of distance between the subject in the foreground, and the background of the image. The shorter the focal length of a lens (wide-angle lens), the stronger the sense of perspective, so that the background appears to extend behind the subject for some distance. Conversely, a lens with a longer focal length (telephoto lens) creates the impression that the distant background is right behind the subject (compression effect), instead of emphasizing perspective.