The greater the difference between a light and the body lighted by
it, the light being the larger, the more vague will be the outlines
of the shadow of that object.
The derived shadow will be most confused towards the edges of its
interception by a plane, where it is remotest from the body casting
it.
195.
What is the cause which makes the outlines of the shadow vague and
confused?
Whether it is possible to give clear and definite outlines to the
edges of shadows.
On the relative size of shadows (196. 197).
196.
THE BODY WHICH IS NEAREST TO THE LIGHT CASTS THE LARGEST SHADOW, AND
WHY?
If an object placed in front of a single light is very close to it
you will see that it casts a very large shadow on the opposite wall,
and the farther you remove the object from the light the smaller
will the image of the shadow become.
WHY A SHADOW LARGER THAN THE BODY THAT PRODUCES IT BECOMES OUT OF
PROPORTION.
The disproportion of a shadow which is larger than the body
producing it, results from the light being smaller than the body, so
that it cannot be at an equal distance from the edges of the body
[Footnote 11: H. LUDWIG in his edition of the old copies, in the
Vatican library--in which this chapter is included under Nos. 612,
613 and 614 alters this passage as follows: _quella parte ch'e piu
propinqua piu cresce che le distanti_, although the Vatican copy
agrees with the original MS. in having _distante_ in the former and
_propinque_ in the latter place. This supposed amendment seems to me
to invert the facts. Supposing for instance, that on Pl. XXXI No. 3.
_f_ is the spot where the light is that illuminates the figure there
represented, and that the line behind the figure represents a wall
on which the shadow of the figure is thrown. It is evident, that in
that case the nearest portion, in this case the under part of the
thigh, is very little magnified in the shadow, and the remoter
parts, for instance the head, are more magnified.]; and the portions
which are most remote are made larger than the nearer portions for
this reason [Footnote 12: See Footnote 11].
WHY A SHADOW WHICH IS LARGER THAN THE BODY CAUSING IT HAS
ILL-DEFINED OUTLINES.
The atmosphere which surrounds a light is almost like light itself
for brightness and colour; but the farther off it is the more it
loses this resemblance. An object which casts a large shadow and is
near to the light, is illuminated both by that light by the luminous
atmosphere; hence this diffused light gives the shadow ill-defined
edges.
197.
A luminous body which is long and narrow in shape gives more
confused outlines to the derived shadow than a spherical light, and
this contradicts the proposition next following: A shadow will have
its outlines more clearly defined in proportion as it is nearer to
the primary shadow or, I should say, the body casting the shadow;
[Footnote 14: The lettering refers to the lower diagram, Pl. XLI,
No. 5.] the cause of this is the elongated form of the luminous body
_a c_, &c. [Footnote 16: See Footnote 14].
Effects on cast shadows by the tone of the back ground.
198.