The text books will all tell you that there are a number of rules for composing a photograph (or a painting for that matter) and it isn’t a bad idea to follow these rules 90% of the time. Working on a newspaper has taught me that simple compositions often work the best and that there are several ways of keeping it simple. One of my favourites is to work with a small depth of field. The human eye will always be drawn to the subject that is in sharp focus with a simple out of focus background. Usually this will mean that the background doesn’t contribute to the image, but every so often an out of focus background forms a really important part of the image.
This picture of three year old boy at a nursery school learning about some creatures that had been brought into the school is a perfect illustration of how throwing the background out of focus gives an enormous boost to the composition and helps to tell the story of the image. The chameleon is in focus, but because the lens (180mm on a 70-200 f2.8 zoom) was wide open at f2.8 the boy becomes an interesting blur. The added 1.6x focal length multiplication brought no change in the depth of field but narrowed the angle down to a 35mm equivalent of 288mm. On this particularly sunny day that meant a shutter speed of 1/4000th of a second on 200 ISO.
Techniques are there to be used, altered, modified and adapted. This one should become really useful to you once you have mastered it. When you are struggling to make an interesting composition it’s always worth considering narrowing your depth of field.