Three Is The Magic Number
Posted by sepial at September 6th, 2006
The length of a image divided by its width is its aspect ratio. The aspect ratio of standard 35mm film is one-and-a-half, that is 3:2. For televisions and for digital sensors it is often 4:3 (Four Thirds).
Interestingly, many useful compositional guidelines are also based around thirds and threes.
Most famously, many artists and photographers swear by the Rule Of Thirds—which is also explained here.
Even when you are interested in only two main subjects in an image, it can gain balance by the inclusion of a third defocused or cropped participant, or by a prominent inanimate object.
When you have three or more main subjects, triangular arrangments can be very effective.
I always use to think the subject had to be smack bang in the centre, but yes, I do see how the third rule gives it that extra something.