Taylor 1715 - Plafond

Brook Taylor, Linear Perspective: Or, a New Method of Representing justly all manner of Objects As they appear to the Eye in all Situations. A work necessary for Painters, Architects, &c. to Judge of, and Regulate Designs by, London [Robert Knaplock] 1715.

pp. 1–2

LINEAR PERSPECTIVE:

SECTION I.

Containing an Explanation of those things that are necessary to be understood in order to the Practice of PERSPECTIVE.

Perspective is the Art of drawing on a Plane the Appearances of any Figures, by the Rules of Geometry.

In order to understand the Principles of this Art, we must consider, That a Picture painted in its utmost degree of Perfection, ought so to affect the Eye of the Beholder, that he should not be able to judge, whether what he sees be only a few Colours laid artificially on a Cloth, or the very Objects there represented, seen thro’ the Frame of the Picture, as thro’ a Window. To produce this Effect, it is plain the Light ought to come from the Picture to the Spectator’s Eye, in the very same manner, as it would do from the Objects themselves, if they really were where they seem to be; that is, every Ray of Light ought to come from any Point of the Picture to the Spectator’s Eye, with the same Colour, the same strength of Light and Shadow, and in the same Direction, as it would do from the corresponding Point of the real Object, if it were placed where it is imagined to be. So that (Fig. 1.) if E T be a Picture, and a b c d be the Representation of any Object on it, and A B C D be the real Object placed where it should seem to be to a Spectator’s Eye in O; then ought the Figure a b c d to seem exactly to cover the Figure A B C D, and the Rays A O, B O, C O, &c. that go from any Points A, B, C, &c. of the original Object to the Spectator’s Eye O, ought to cut the Picture in the corresponding Points a, b, c, &c. of the Representation. Wherefore, in order to demonstrate any Proposition in this Treatise, upon this Principle, I always suppose the real original Object to be placed where it should appear to be.