There are lots of numbers that come into play when it comes to photography: shutter speeds, f-stops, lens focal lengths, digital sensor multiplying factors and fill flash ratios are some of the obvious. One number that doesn’t often pop into photographers’ minds is the number of subjects in a photo. The importance behind this deals with composition. There’s a compositional fact that states: When including an even number of similar subjects, it is more difficult to create a successful composition than when an odd number of subjects appear. The obvious even number that comes to mind is two. Unless it relates to people, when two subjects are the primary elements in a photo, they compete with one another for attention. When...