Trade Tricks: The Selective Focus Technique
A key photographic technique to distinguish your subject from its surroundings
One of the challenges we face as photographers is making the subject stand out from its surroundings. An effective way to do this is to use the selective focus technique, which allows us to choose one part of the image to be sharp and in focus while making the rest out of focus. It's the opposite of getting a lot of depth of field. While this technique lets the viewer know what's important in the photo, it's also a way to make interesting compositions that can't be duplicated any other way.
It's possible, and often useful, to create this effect in the computer by selecting one part of the photo, keeping it sharp and blurring the rest. Shooting the image with selective focus from the start has advantages, however: You spend less time on your photo in the computer; your composition better fits the in- and out-of-focus areas; the effect always looks natural (because it is); edges are never a problem (the computer-generated effect can be difficult with edges); there's no problem with the "wrong" elements being sharp or unsharp; and transitions always look right.
Selective focus is accomplished with the following steps.
1. Choice Of ƒ-Stop. Choose your widest ƒ-stops, such as ƒ/2.8 or ƒ/4 (depending on the lens and focal length). Wide apertures minimize depth of field. You'll need fast shutter speeds to balance this ƒ-stop in bright light. You also may need a neutral-density filter (a dark gray filter) to allow you to use wide ƒ-stops.