How the Eye Sees Simply: Flat versus Curved Perspective Screens
Three lit spheres and a displaced viewpoint projected onto plane and curved screens
The folio examines how images fall differently on a flat screen and a curved one. A first diagram projects three half-lit spheres a, b, c through a central viewpoint onto a planar screen K and a curved screen, and a second, with the viewpoint m displaced to one side, shows how a flat screen distorts equal intervals o v and v x while a curved screen keeps them regular. The notes state that a nearer thing looks larger than an equal thing farther off, and advise viewing such a perspective from a single hole at m or from at least three times the object's size. A reclining figure and further cursive text, only partly transcribed, share the lower sheet.
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Three lit spheres on flat screen K and a curved screen
Rays from three half-lit spheres a, b, c converge symmetrically to a point 5 at the center of a curved screen. They cut the flat screen K at d/e, f/g and h/l, and the curved screen at n/m, s/t and v/x, so the same objects are recorded at different spacings on the two surfaces.
The nearer of two equal things looks larger
A thing closer to the eye always appears larger than another of equal quality that is farther away. This is the visual principle underlying the difference between the flat and curved screens shown above.
Eye at m: equal spaces o v and v x distorted on a flat screen
With the eye at m, the equal spaces o v and v x look almost identical, yet raised onto the flat screen n o they map to the very unequal segments o r and r Q, because the low eye foreshortens them. A curved screen o p, always equidistant from the eye, renders such things well; one should therefore view from a single hole at m, or stand at least three times the object's size away.