On painting. A most important part of painting is the backgrounds of the things depicted, against which backgrounds the outlines of natural bodies that have a convex curvature are always recognized — the shapes of such bodies against those fields — even though the colors of the bodies are the same color as the said field. And this comes about because the convex edges of the bodies are not lit in the same way as the same light lights the background, for such an edge will often be lighter or darker than the field itself. But if such an edge is of the color of that field, without doubt that part of the painting will prevent the shape of that edge from being known; and this kind of choice in painting is to be shunned by the minds of good painters, since the painter's intention is to make his bodies appear forward of the fields, while in the case described above the contrary happens — not only in painting but in things in relief.