There are a thousand proofs that the old masters and all good painters
from Raphael onwards executed their frescoes from cartoons and their
little easel pictures from more or less finished drawings.... Your model
gives you exactly what you want to paint neither in character of drawing
nor in colour, but at the same time you cannot do without him.
To paint Achilles the most goodly of men, though you had for your model
the most abject you must depend on him, and can depend on him for the
structure of the human body, for its movement and poise. The proof of
this is that Raphael used his pupils in his studies for the movements of
the figures in his divine pictures.
Whatever your talents may be, if you paint not from your studies after
nature, but directly from the model, you will always be a slave and your
pictures will show it. Raphael, on the contrary, had so completely
mastered nature and had his mind so full of her, that instead of being
ruled by her, one might say that she obeyed him and came at his command
to place herself in his pictures.
_Ingres._