Good composition is something I liken to an old fashioned legal balance. If too much emphasis is placed on either the left or right side, the scale tips due to uneven weight distribution. The same holds true in a photograph. If the composition has too much subject matter on one side and not enough on the other, the balance is thrown off. This unevenness causes the viewer to concentrate on one part of the image and wonder why another section is void of important information.
The size of the subjects do not always dictate the balance. For instance, a large neutral colored object may appear on the right and a small vividly colored object on the left. Even though the vivid object takes up less image real estate, it can easily command more attention due to its color. With this in mind, don’t feel obligated to balance compositional elements solely on their magnitude.
A successfully created composition is one in which the viewer can let their eyes flow through the photograph without feeling compelled to return to a specific spot because there’s too much weighting on a particular side. When creating a composition, the key is to look beyond the main focal point. The supporting material to the left, right, top, bottom, front, and behind the main subject is equally as important. No matter how good the lead actor is, if the supporting cast is weak, the movie will fall short. This analogy holds true for a photograph.
Elements of balance to consider when creating a composition are dark vs light objects, the number of near vs far elements, and the range of focus regarding how much depth of field is or is not integrated. Out of focus areas command less attention than those rendered sharp. As stated above, the weighting of the subject based on color also needs to be considered. Another factor is texture. Smooth objects attract the eye less than patterned or those with relief. For instance, a sky with puffy cumulous clouds will attract the viewer’s eye more than one that’s clear. So before you press the shutter, study the viewfinder to see if your composition looks lopsided based on the above factors. If not, you’ve achieved balance.