The Painter in oil

Diffused Light. - Much of the characteristic quality of out-door light is the result of
the diffusion of light due to both the refraction and the reflection of the sky. The light
which bathes the landscape comes in all directions from the sky. Necessarily, then, the
sky will be in most cases far higher in value than anything under it. Even the blue of the
sky, which looks darker than some bit of light in the landscape, you will find, if you can
manage to get them to tell against each other, will be the more luminous of the two, and
will look lighter. There are times when the sun glares on a white building or a piece of
white sand, when the white tells light against the blue. But these are exceptions, and if
we could get a blue paint which would give the intensity of color, and also the brilliancy
of the light, even these cases would be most truly represented with the sky as the higher
value. It is a case of whether to sacrifice value to color, or the reverse, as we cannot have
both
Sometimes, however, in a storm, the dense dark of the storm sky is really lower in
value than some white object against it, especially if there be a bit of sun breaking
through on it.
But in general, nevertheless; you should consider the sky as always lighter and more
luminous than anything under it.
Three Planes. - It will help you in understanding the way the light falls on landscape
to consider everything as in one of three planes, and these planes taking greater or less
proportions of light according to the posit ion of the sun with reference to them.
The position of the sun changes from a point immediately over, to a point practically
at right angles to all objects in nature. Everything that can exist under the sun will come
in one of these planes, and at some time in the day in each.
The vertical, the horizontal, or some sort of an oblique between these two. If the sun is
overhead exactly, the flat ground, the tops of trees and houses, will get the full amount of
sunlight. The vertical planes, sides of houses, depths of foliage, etc., will get the least,
some of them being lighted only by diffused and reflected light. The planes lying between
these two extremes will get more or less, according as they are more or less at right
angles to the direct rays of the sun. And as the sun declines from the zenith, the vertical
planes get more and more and the horizontal planes less and less of the light, till in the
late afternoon the banks of trees and sides of buildings and cloud masses are gilded with
light, al1d the broad horizontal plains of land al1d water are in shadow.
However obscured the sun may be, this principle holds more or less; and it makes
clear and helps you to observe and notice many facts in landscape light and shade which
it is necessary to know.
Millet said that all the beauty of color and value, and the whole art of painting, rested
on the comprehension and observance of these facts.
He said that as the planes of any form turned towards or away from the light and so
got more or less of it, and as one form stood more or less far back of another and the
atmosphere came between, the color and value changed; and in the observance of this,
and its representation as applied to any and every object or group of objects, lay the
whole of painting. All the possible beauties of the art rested on it. He showed a painting
of a single pear in which these things were most subtly observed, and said that that
painting was as complete and perfect as any painting he could do simply because in the
observance of these relations was implied the observance of everything which was vital
to painting.