Perspective

Perspective Introduction Two types of projections or methods of realistically representing objects on a page are parallel projection and perspective or central projection. Parallel projection is used for technical drawings and blueprints and is covered in the next chapter. Perspective or central projection is used in creative art or technical sketching but seldom in technical drawing. Perspective or Perspective projection, sometimes called central projection, is the method by central which artists realistically portray three-dimensional objects on a two- projection dimensional plane. Perspective or central projection is, in theory, where objects are drawn on a page by extending lines of sight called projectors from the eye of the observer through lines and points on the object to the plane of projection. The resultant drawing is always called a central projection because the lines of sight or projectors meet at a central point -the eye of the observer. The projected view of the object may vary considerably in size according to the relative positions of the objects and the plane of projection. Varying from natural perspective distorts images into abstract or expressive representation. Perspective alone will not effectively create the illusion of three dimensions without tone or shading. In photography, perspective dominates. Although scene replication is almost exact, photography has crucial limitations regarding field of view. The human eye sees wide and far but the photographic lens has field of view limitations that even with corrective lenses results in distortion. Corrective wide-angle lenses typically result in distortion called barrel distortion, where the lines parallel to the sides of the picture frame bow inward at the center. Figure 5-1 illustrates the effect of barrel distortion. Figure 5-1.—Differences in a cube exhibiting: A. Normal perspective, and B. Barrell distortion. Continued on next page 5-3