Sir Joshua Reynolds tells us it was his habit in looking for the secrets of the masters of painting to make rough pencil notes of those pictures that attracted him by their power of effect as he passed from one gallery to another. He found almost all of them revealed a broad middle tone which was divided again into half dark and half light tones, and these, added to the accents of light and dark _made five distinct tones._ The Venetian painters attracted him most and, he says, speaking of Titian, Paul Veronese and Tintoret, “they appeared to be the first painters who reduced to a system what was before practised without any fixed principle.” From these painters he declares Rubens extracted his scheme of composition which was soon understood and adopted by his countrymen, even to the minor painters of low life in the Dutch school.
“When I was in Venice,” he says, “the method I took to avail myself of their principle was this: When I observed an extraordinary effect of light and shade in any picture I darkened every part of a page in my note-book in the same gradation of light and shade as the picture, leaving the white paper untouched to represent light and this without any attention to the subject or the drawing of the figures. A few trials of this kind will be sufficient to give the method of their conduct in the management of their lights. After a few experiments I found the paper blotted nearly alike: their general practice appeared to be _to allow not above a quarter of the picture for light, including in this portion both the principal and secondary lights; another quarter to be as dark as possible and the remaining half kept in mezzo-tint or half shadow._”
“Rubens appears to have admitted rather more light than a quarter and Rembrandt much less, scarce an eighth; by this conduct Rembrandt’s light is extremely brilliant, but it costs too much; the rest of the picture is sacrificed to this one object. That light will certainly appear the brightest which is surrounded with the greatest quantity of shade, supposing equal skill in the artist.”
“By this means you may likewise remark the various forms and shapes of those lights as well as the objects on which they are flung; whether a figure, or the sky, a white napkin, animals, or utensils, often introduced for this purpose only. It may be observed likewise, what a portion is strongly relieved and how much is united with its ground; for it is necessary that some part (though a small one is sufficient) should be sharp and cutting against its ground whether it be light on dark, or dark on a light ground, in order to give firmness and distinctness to the work. If, on the other hand, it is relieved on every side, it will appear as if inlaid on its ground.”