On Derived Shadow: Its Strength and Cutting
A red-chalk note under the heading 'Painting' on how derived shadow gains power
Under the heading 'Painting', this red-chalk page sets down three rules on derived (cast) shadow. Leonardo states that derived shadow is the more powerful the nearer it lies to its origins, that a given quality of shadow appears stronger the closer it is to the eye, and that the 'percussion and cutting' of a derived shadow is darkest where it is shortest. The whole page is mirror-script in faded red chalk with no diagram.
On this page
Three rules on the strength of derived shadow
Derived shadow grows more powerful as it approaches its origins, and a single quality of shadow looks stronger the nearer it stands to the eye. Where the derived shadow strikes and is cut off, it is darkest when that cut is shortest. The notes belong to Leonardo's science of light and shade for painting.
Shadow strength as a function of distance
The observations treat cast shadow as a measurable physical effect: its intensity depends on nearness to its source and on the distance of the shadow from the observing eye. This links the practice of shading pictures to the optics of light and shade.