PERSPECTIVE

(Lat. perspicio, I look through.) In the Fine Arts, the art of delineating on a given transparent plane or superficies objects as they appear to an eye placed at a given height and distance. From the definition, it is evident that to delineate the true appearance of an object on a plane surface, it becomes nece ary to know the laws according to which the apparent linear dimensions of an object increase or decrease; and they are these generally: — 1. The visual angle, or the apparent magnitude of a line, will be le the greater the distance, and the converse; 2. It will be le the more obliquely a line is viewed; 3. The law of diminution will be nearly in proportion to the obliquity and distance conjointly. In the following diagram, let the eye of the spectator be at I, and let E F G Hbc the plane on which the appearance of objects is observed. This is called the perspective plane, or plane of the picture. Now the appearance of every object to be delineated will vary according to the plane in which it stands, considered witn respect to the perspective plane; hence the particular situations of object planes are the main points for consideration. It is manifest that any plane pa ing through the eye can only be seen on the perspective [s. 927]