If you want to acquire facility for bearing in mind the expression
of a face, first make yourself familiar with a variety of [forms of]
several heads, eyes, noses, mouths, chins and cheeks and necks and
shoulders: And to put a case: Noses are of 10 types: straight,
bulbous, hollow, prominent above or below the middle, aquiline,
regular, flat, round or pointed. These hold good as to profile. In
full face they are of 11 types; these are equal thick in the middle,
thin in the middle, with the tip thick and the root narrow, or
narrow at the tip and wide at the root; with the nostrils wide or
narrow, high or low, and the openings wide or hidden by the point;
and you will find an equal variety in the other details; which
things you must draw from nature and fix them in your mind. Or else,
when you have to draw a face by heart, carry with you a little book
in which you have noted such features; and when you have cast a
glance at the face of the person you wish to draw, you can look, in
private, which nose or mouth is most like, or there make a little
mark to recognise it again at home. Of grotesque faces I need say
nothing, because they are kept in mind without difficulty.
The position of the head.
573.
HOW YOU SHOULD SET TO WORK TO DRAW A HEAD OF WHICH ALL THE PARTS
SHALL AGREE WITH THE POSITION GIVEN TO IT.
To draw a head in which the features shall agree with the turn and
bend of the head, pursue this method. You know that the eyes,
eyebrows, nostrils, corners of the mouth, and sides of the chin, the
jaws, cheeks, ears and all the parts of a face are squarely and
straightly set upon the face.
[Footnote: Compare the drawings and the text belonging to them on
Pl. IX. (No. 315), Pl. X (No. 316), Pl. XL (No. 318) and Pl. XII.
(No. 319).]
Therefore when you have sketched the face draw lines passing from
one corner of the eye to the other; and so for the placing of each
feature; and after having drawn the ends of the lines beyond the two
sides of the face, look if the spaces inside the same parallel lines
on the right and on the left are equal [12]. But be sure to remember
to make these lines tend to the point of sight.
[Footnote: See Pl. XXXI, No. 4, the slight sketch on the left hand
side. The text of this passage is written by the side of it. In this
sketch the lines seem intentionally incorrect and converging to the
right (compare I. 12) instead of parallel. Compare too with this
text the drawing in red chalk from Windsor Castle which is
reproduced on Pl. XL, No. 2.]
Of the light on the face (574-576).
574.
HOW TO KNOW WHICH SIDE OF AN OBJECT IS TO BE MORE OR LESS LUMINOUS
THAN THE OTHER.
Let _f_ be the light, the head will be the object illuminated by it
and that side of the head on which the rays fall most directly will
be the most highly lighted, and those parts on which the rays fall
most aslant will be less lighted. The light falls as a blow might,
since a blow which falls perpendicularly falls with the greatest
force, and when it falls obliquely it is less forcible than the
former in proportion to the width of the angle. _Exempli gratia_ if
you throw a ball at a wall of which the extremities are equally far
from you the blow will fall straight, and if you throw the ball at
the wall when standing at one end of it the ball will hit it
obliquely and the blow will not tell.
[Footnote: See Pl. XXXI. No. 4; the sketch on the right hand side.]
575.
THE PROOF AND REASON WHY AMONG THE ILLUMINATED PARTS CERTAIN
PORTIONS ARE IN HIGHER LIGHT THAN OTHERS.
Since it is proved that every definite light is, or seems to be,
derived from one single point the side illuminated by it will have
its highest light on the portion where the line of radiance falls
perpendicularly; as is shown above in the lines _a g_, and also in
_a h_ and in _l a_; and that portion of the illuminated side will be
least luminous, where the line of incidence strikes it between two
more dissimilar angles, as is seen at _b c d_. And by this means you
may also know which parts are deprived of light as is seen at _m k_.
Where the angles made by the lines of incidence are most equal there
will be the highest light, and where they are most unequal it will
be darkest.