Now I enter what Ingres called the ” probity” of art. Having suggested to a friend that they treat edges with more consideration i did a little drawing. Of a mandarin.
The outline silhouette is a beginning. Then we consider the difference between surfaces that turn away rapidly or slowly. Do we render this by blurring the slow and sharpening the rapid? Or do we darken the sharp and lighten the gentle? The temptation is to do both,but if you use a tonal signifier this will invariably run counter to any rendering of light.
Michael Grimaldi at the Art Students League in New York introduced me to a kind of graded wash of hatching,using a pressure change( and hence,tonal change). This has its use rendering edges, I find.
There are internal and external edges.
The internal are the plane changes,and since most planes are curved,Grimaldi’s graduated hatching is useful.
The external edges are infernal because they belong to the object ( its silhouette) and to the background simultaneously. Any tonal or colour change from object to background,and we have a dilemna ,not just an edge.
And its only a drawing of a mandarin!
In painting and drawing,bounced reflected light and crevice shadow can be ally or enemy in edges but you must decide what side they are on,silhouette or background. Or do you show a seamless transition and have what is called a ‘lost’ edge. The sharp hard edge , the “found” edge projects forward in pictorial space, the soft recedes. Of course the various edges are not all contained by one object.,the hard edge of one may cut across another object with its soft edge ,creating dramatic illusions of 3d space
It is worth mentioning that the penumbra is usually soft (blurry) the crevice shadow sharp, and softer external edges appear at the sides and top alongside sharper edges. The core or crescent shadow at its edges will reveal the internal surface it traverses , with rapid plane shifts and slow ones, and simultaneously describing the transitions into form shadow dark and half light.
There is no chance atmospheric perspective can apply in this restricted space,but the convention can. Assume our mandarin is spherical,and cut in half vertically, displaying a circle facing us. For the front half, we could assume every edge ,internal and external belongs to the mandarin. But the back half shows only “top half”edges and the externals belong with the background which is often at some distance compared with the bottom half background.
This allows application of atmospheric perspective devices such as narrowing tonal range,loss of yellow,loss of detail,setting hard edge against soft to create depth ,etc.
Such devices almost subvert the act of perception,but purists only need refrain.
And let me dispell any notion that this is a scientific analysis of a rational process.Its not. It is not a substitute for the hard work of observing specific unique events then applying poetic means to make coherent sense of it all.While we have been pondering , I notice my mandarin has turned into a painting. That’s magic,not science.