deceived in his own work.  And if you are not conscious of this in yourself study it in others and profit by their faults.  Therefore be curious to hear with patience the opinions of others, consider and weigh well whether those who find fault have ground or not for blame, and, if so amend; but, if not make as though you had not heard, or if he should be a man you esteem show him by argument the cause of his mistake.

On the limitations of painting (533-535)

533.

HOW IN SMALL OBJECTS ERRORS ARE LESS EVIDENT THAN IN LARGE ONES.

In objects of minute size the extent of error is not so perceptible as in large ones; and the reason is that if this small object is a representation of a man or of some other animal, from the immense diminution the details cannot be worked out by the artist with the finish that is requisite.  Hence it is not actually complete; and, not being complete, its faults cannot be determined.  For instance:  Look at a man at a distance of 300 braccia and judge attentively whether he be handsome or ugly, or very remarkable or of ordinary appearance.  You will find that with the utmost effort you cannot persuade yourself to decide.  And the reason is that at such a distance the man is so much diminished that the character of the details cannot be determined.  And if you wish to see how much this man is diminished [by distance] hold one of your fingers at a span’s distance from your eye, and raise or lower it till the top joint touches the feet of the figure you are looking at, and you will see an incredible reduction.  For this reason we often doubt as to the person of a friend at a distance.

534.

WHY A PAINTING CAN NEVER APPEAR DETACHED AS NATURAL OBJECTS DO.

Painters often fall into despair of imitating nature when they see their pictures fail in that relief and vividness which objects have that are seen in a mirror; while they allege that they have colours which for brightness or depth far exceed the strength of light and shade in the reflections in the mirror, thus displaying their own ignorance rather than the real cause, because they do not know it.  It is impossible that painted objects should appear in such relief as to resemble those reflected in the mirror, although both are seen on a flat surface, unless they are seen with only one eye; and the reason is that two eyes see one object behind another as a and b see m and n. m cannot exactly occupy [the space of] n because the base of the visual lines is so broad that the second body is seen beyond the first.  But if you close one eye, as at s the body f will conceal r, because the line of sight proceeds from a single point and makes its base in the first body, whence the second, of the same size, can never be seen.