Small windows, black surfaces, and the effect of distance
How light-to-shadow contrast depends on the light, the colour, and remoteness
Continuing the theory of light and shade in Part Five of the Treatise on Painting. Leonardo notes that light from small windows into a large room produces a harsh contrast that should not be used, and that black surfaces show the least difference between their lit and shadowed parts since both read as black. He then argues that a shadowy body seen from far off shows less contrast between its lights and shadows than when near, because the luminous air interposed between eye and body is thicker over the greater distance.
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Light from small windows makes a harsh contrast
Lights made by small windows produce a great difference between lights and shadows, and especially if the room they light is large. This effect is not good to use.
Black surfaces vary least between light and shadow
A black surface, and those which partake more of blackness, has the least difference between its shadowed and its luminous parts of any surface. Because the illuminated part still shows itself black and the shadowed part can only be black, it gains just a little more darkness than the lit black part.
Distance flattens the contrast of a shadowed body
A shadowy body will show less difference between its lights and shadows the more remote it is from the eye, and more difference when it is near. This is because the clarity of the luminous air interposes with greater thickness between the eye and the shadowy body when it is remote than when it is near.