What Shape Canvas is needed

This painting is available on an eBay auction for seven days, click here.

This 4x5 inch oil on canvas was done on my lap sitting by a stream on a gray day. The stream feeds into the Mississenwa River in Indiana. The gray day muted the colors and deadened the highlights in the deep woods. The orange comes from the fresh bed of leaves on the ground -- the rains had not yet turned them into a black tea.

The shape of a canvas is mostly determined by what I'm comfortable painting on. Some artists prefer square canvases over rectangles, and some have an affinity for long or narrow canvases. Not always, but usually I will pick sizes that are considered traditional or ready-made. This is because the frames for these are substantially cheaper. Ready-made frames can be half the price of a custom frame.

With that said, it is important to remember that an artist usually will pick a canvas shape that fits the subject. As an artist, if I try to make a scene fit the canvas rather than use a canvas with proportions that fit the scene, then I'm generally not as happy with the end results.
Like many artists, I carry with me two "L" shaped pieces of cardboard. On each leg of the cardboard I have marked various sizes in inches. When I put the two "L"s together to form a frame, I can slide them to the marks to match the proportions of the canvas I am using. Then I can look through this cardboard frame at my scene and eliminate all the things I don't want in the picture. For years artists have used their index fingers and thumbs of both hands to create a frame or taken paper and cardboard frames into the field with them to aid in fitting what they are painting onto the canvas