I had been a full time painter for many years before I really started to give edges their due. I was painting last week with my good friend, Janice Robertson, and we were discussing how giving edges the attention they deserve is not something we considered earlier on in our development as painters.
As the years passed, I gradually took more notice that the paintings that really seemed masterful to me took full advantage of a full variety of edges.
Notice in the painting above that foreground shapes have harder edges, rounded objects (tree trunks) have soft edges, and much of the complexity of the foliage is suggested by VERY soft edges, especially against the light of the sky. Edges are really important, it turns out.
Edges are "softened" either by making gradual tonal transitions into other areas, or by allowing the edges on two contrasting areas to mingle by painting wet into wet, which is my personal favorite.
Try studying some paintings you love and take notice of how sharp edges draw the eye and lost or soft edges create the illusion of depth and suggest some mystery. The eye loves it! Also notice how explaining the texture of grass, leaves, etc., can be accomplished by explaining texture only on the edges of the mass....it's a great way to say time when in the field. Less is more.
Happy painting all,