The easiest way to describe edge without going into too much technical detail I am going to pull from Kevin's book again. The book is "A Visual Palette."
"Edge is an effective tool for blending or separating contiguous shapes. Ad the boundary between shapes, an edge acts like a fence, which may be tall and intimidating or low and more accessible. Edges come in a variety of sharpness and softness. A sharp, bold edge works like a solid brick fence: it restrains the eye and confines it within a given shape. When an edge is completely annihilated, it allows the eye to freely access adjacent shape."
John Singer Sargent |
the other more obvious lost edge is his right trouser leg right below the knee where there is no discernible edge or line yet your eye does not lose its way and the leg is still there. The hard edges are beautiful here too with a wonderful flow of the figures stance giving us, the viewer an insight into the man's personality.