Those likenesses will be retained more in the eye that are born of a more luminous body.

Perspective. Every body larger than the space between the pupils, which must be judged by the eye, will be four times its own size distant. And if it be smaller than the interval of light between the pupils, nothing nearer will be comprehended by the eye, unless four times the distance of the interval between the pupils be set between the eye and the thing seen by it.

a - o – n f b – p c - e. Proof that perspective, the office of the eye, does not reduce to a point. The reason is this: if you set near the eye a thing much smaller than the pupil, you will see, beyond that obstruction, each thing as if the interposed thing were transparent. Let us say the pupil is o p and that the point imagined by the perspectivists is n. Now do you not see that if you set before it the thickness f, the place b c will be occupied by that f? Whence experience... Everything transparent between a e, which is not a point but the whole pupil, is equal in visual power, but not equal in potency, because that part which is more distant from its centre discerns things less. The visual power being equally infused through the pupil, no thing of smaller quantity than it, set closely before it, can occupy any part of the distant object. You shall make the proof thus: let o p be the pupil, f the smaller thing set before it, a e the distant object. Draw the line o e over the obstruction f, and likewise the line n b: see that the half-pupil o n sees all of b e, and likewise the other half sees a c; and by this it is shown that if the point n alone were to see, the first object f would occupy for the eye the whole part b c of the second object. Again it is confirmed that all the species of the objects enter the eye upside down: beyond f, see that b, above, is below at n e, and that which is below answers above at o.

c b a – f d - n. It is impossible that by any distance the luminous body can illuminate the middle of the opaque spherical body, showing why the angles a d b and b c f cannot be equal upon the central line b n.

The nearer the luminous body is to the shadowed one, the more it illuminates it, the luminous body being larger than the opaque. The nearer the luminous body is to the shadowed one, the less it will illuminate it, if that luminous body is smaller than the shadowed one. But the more the luminous body, smaller than the shadowed one, is distant from that shadowed body, the more it will illuminate it. And if the luminous body larger than the shadowed one is moved away from the shadowed one, it will always diminish the total illuminated, down to near the middle.