Perspective
Collier's New Encyclopedia (1921)
the science of repre senting appearances, and as such is opposed to geometry, which is the science of representing facts. It is founded upon such rules as can be deduced from the facts which are discovered by looking at objects through a sheet of glass glass or other transparent medium placed upright between the object and the observer. It is found when objects are so looked at that their apparent form is very different from their real one, both as regards shape and distinctness. The portion of the subject which deals with the changes in form is absolutely scientific; it is called linear perspective. The changes in distinctness are effected by distance and atmosphere, and differ constantly with different conditions of light and atmosphere. It is the purely artistic side of the science which is called aërial perspective, and success in its application depends on the individual ability of the artist. The chief point with which linear perspective ive has to deal is the apparent diminution in size of objects as they recede from the spectator. A practical knowledge of the science is absolutely a necessity for a successful artist. tist A kind of painting designed expressly to deceive the sight by representing the continuation of an alley, a building, a the like. Oblique (or landscape, or angular) perspective, where the plane of the picture is supposed to be at an angle to the side of the principal object in the picture, as, for instance, a building. Parallel perspective, where the plane of the picture is parallel to the side of the principal object in the picture. Perspective plane, the surface on which the objects are delineated, or the picture drawn. It is supposed to be placed vertically between the eye of the spectator and the object. Also termed the plane of projection, or the plane of the picture.
What Has Changed in the Last Century
The geometry Collier's set out in 1921 is still exactly what is taught: the vanishing point, the picture plane held upright between eye and object, and the distinction between linear and aërial perspective have not moved. What has moved is the claim that "a practical knowledge of the science is absolutely a necessity for a successful artist" — Picasso and Braque had already dismantled the single viewpoint before 1921, and Erwin Panofsky's essay of 1927, Perspective as Symbolic Form, argued that Renaissance perspective was a cultural convention rather than a neutral record of how the world looks. The other large change is who does the work: the same construction is now carried out by hand only in drawing classes, and otherwise by the perspective-projection matrix inside every camera lens simulation, CAD package and video game renderer.
Written for this edition, 2026.