A constant is something that can't be readily changed, against which other things can be compared, measured, or contrasted. In painting, the constants are the sides and corners of the actual canvas. There are four straight edges and four 90 degree angles that cannot be ignored. Dealing with these can manifest itself in a variety of ways. The far left tree in this painting, oil on canvas, 20 by 16", could be seen as an echo or acknowledgement of the line created by that side of the canvas. Corners can pose an even greater challenge, as two sides of a triangle are already formed. Looking at the upper right corner here, the three light trees could be said to each form a shape in conjunction with the outer edge of the canvas. Did I choose these particular tree placements because they interacted with the sides and corners? How much of a painting is set aside to deal with the borders of the canvas?