A quick and effective way to work out the best composition for any scene is to hold up a couple of L-shaped pieces of cardboard to form the correct proportions of your canvas. As you look through this instant viewfinder, study the possibilities. What happens, for example, if you place the center of interest near the edge? How does the mood change from a tightly cropped composition to one with generous space on one or all sides? Is a vertical format preferable over a horizontal one? Simple compositional changes can alter the entire emotional impact of your painting.