Depth of Field

The perspective-flattening of long lenses can also be used in other circumstances, because they also have the effect of reducing depth of field. You can use this to isolate a subject against its background by blurring it out, as in the shot below.

Compare this with the same shot but taken with a wide angle lens from a much closer range. The relative size of the statue is the same in both shots, but due to the increased depth of field in the wide angle shot, the background, although apparently more distant, is much sharper.

Because of this reduced depth of field, careful focusing with a long telephoto lens can pick out individual subjects amidst cluttered surroundings, such as a single person in a crowd. Note also that the perspective-compression effect makes the street look a lot busier than it really is.

The same scene shot from the same position using a wide angle lens shows the street (High Street in Exeter) in a very different way.

The examples I’ve used here are extremes, which I have done to emphasise the effects I’m attempting to demonstrate, but in truth a lot of people will only ever use their zoom lenses at either maximum or minimum settings. Don’t do this out of habit; instead use the full range of the lens to explore all the different possibilities it offers. A focal length is a useful creative tool, so make the most of it.

Ravi Kant Gupta

December 24, 2012, 5:16 pm

Very informative. However, effects of aperture size on focal length would be excellent.

comments powered by Disqus