[Footnote:  This passage contains the solution of the problem proposed in No. 29, lines 10-14.  Leonardo was evidently familiar with the law of optics on which the construction of the stereoscope depends.  Compare E. VON BRUCKE, Bruchstucke aus der Theorie der bildenden Kunste, pg. 69:  “Schon Leonardo da Vinci wusste, dass ein noch so gut gemaltes Bild nie den vollen Eindruck der Korperlichkeit geben kann, wie ihn die Natur selbst giebt.  Er erklart dies auch in Kap.  LIII und Kap.  CCCXLI (ed.  DU FRESNE) des ‘Trattato’ in sachgemasser Weise aus dem Sehen mit beiden Augen.”

Chap. 53 of DU FRESNE’S edition corresponds to No. 534 of this work.]

535.

WHY OF TWO OBJECTS OF EQUAL SIZE A PAINTED ONE WILL LOOK LARGER THAN
A SOLID ONE.

The reason of this is not so easy to demonstrate as many others.  Still I will endeavour to accomplish it, if not wholly, at any rate in part.  The perspective of diminution demonstrates by reason, that objects diminish in proportion as they are farther from the eye, and this reasoning is confirmed by experience.  Hence, the lines of sight that extend between the object and the eye, when they are directed to the surface of a painting are all intersected at uniform limits, while those lines which are directed towards a piece of sculpture are intersected at various limits and are of various lengths.  The lines which are longest extend to a more remote limb than the others and therefore that limb looks smaller.  As there are numerous lines each longer than the others—­since there are numerous parts, each more remote than the others and these, being farther off, necessarily appear smaller, and by appearing smaller it follows that their diminution makes the whole mass of the object look smaller.  But this does not occur in painting; since the lines of sight all end at the same distance there can be no diminution, hence the parts not being diminished the whole object is undiminished, and for this reason painting does not diminish, as a piece of sculpture does.

On the choice of a position (536-537)

536.

HOW HIGH THE POINT OF SIGHT SHOULD BE PLACED.

The point of sight must be at the level of the eye of an ordinary man, and the farthest limit of the plain where it touches the sky must be placed at the level of that line where the earth and sky meet; excepting mountains, which are independent of it.

537.

OF THE WAY TO DRAW FIGURES FOR HISTORICAL PICTURES.

The painter must always study on the wall on which he is to picture a story the height of the position where he wishes to arrange his figures; and when drawing his studies for them from nature he must place himself with his eye as much below the object he is drawing as, in the picture, it will have to be above the eye of the spectator.  Otherwise the work will look wrong.

The apparent size of figures in a picture (538-539)