The surface of a body assumes in some degree the hue of those around
it. The colours of illuminated objects are reflected from the
surfaces of one to the other in various spots, according to the
various positions of those objects. Let _o_ be a blue object in full
light, facing all by itself the space _b c_ on the white sphere _a b
e d e f_, and it will give it a blue tinge, _m_ is a yellow body
reflected onto the space _a b_ at the same time as _o_ the blue
body, and they give it a green colour (by the 2nd [proposition] of
this which shows that blue and yellow make a beautiful green &c.)
And the rest will be set forth in the Book on Painting. In that Book
it will be shown, that, by transmitting the images of objects and
the colours of bodies illuminated by sunlight through a small round
perforation and into a dark chamber onto a plane surface, which
itself is quite white, &c.
But every thing will be upside down.
Combination of different colours in cast shadows.
272.
That which casts the shadow does not face it, because the shadows
are produced by the light which causes and surrounds the shadows.
The shadow caused by the light _e_, which is yellow, has a blue
tinge, because the shadow of the body _a_ is cast upon the pavement
at _b_, where the blue light falls; and the shadow produced by the
light _d_, which is blue, will be yellow at _c_, because the yellow
light falls there and the surrounding background to these shadows _b
c_ will, besides its natural colour, assume a hue compounded of
yellow and blue, because it is lighted by the yellow light and by
the blue light both at once.
Shadows of various colours, as affected by the lights falling on
them. That light which causes the shadow does not face it.
[Footnote: In the original diagram we find in the circle _e_
"_giallo_" (yellow) and the cirle _d_ "_azurro"_ (blue) and also
under the circle of shadow to the left "_giallo_" is written and
under that to the right "_azurro_".
In the second diagram where four circles are placed in a row we find
written, beginning at the left hand, "_giallo_" (yellow), "_azurro_"
(blue), "_verde_" (green), "_rosso_" (red).]
The effect of colours in the camera obscura (273-274).
273.
The edges of a colour(ed object) transmitted through a small hole
are more conspicuous than the central portions.
The edges of the images, of whatever colour, which are transmitted
through a small aperture into a dark chamber will always be stronger
than the middle portions.
274.