ABSTRACT
The perspective literally means ‘to look through’, and an accurate record or facsimile of the spatial relationships of objects in a scene is given by placing a glass plate, the picture plane, in the observer’s field angle of view and tracing the necessary outlines thereon. The orthogonal distance between the picture plane and viewpoint is the principal distance of the perspective record. The convergent rays form a central perspective and continue undeviated and divergent beyond the viewpoint to an image plane which is conjugate to the subject plane. In pictorial terms, a near viewpoint gives a ‘steep’ perspective with large changes of scale in a subject, while a distant viewpoint gives a ‘flattened’ perspective with only small changes of scale even in a subject of some depth. The centre of perspective is the centre of the entrance pupil for object space and the centre of the exit pupil is the centre of projection for projection into image space.
