11-17-2009, 08:19 AM
"When your photographic vision calls for its use."
11-17-2009, 08:29 AM
"WHY SHOULD I do it?"
To emphasize the subject, or some specific part of it; to draw the viewer's eye to something which caught your eye in the first place.
11-17-2009, 10:04 AM
For me, it's all about making the image feel right. I'm always trying to invoke an emotional response; the technique has to support that emotion. Sometimes that means sharpness and extra contrast, and sometimes that means shallow depth of field and/or lack of real focus. Diffusion, front focus, shooting through vaseline- or dirt-covered filters, etc, are used when it helps me communicate emotion.
Technique for technique's sake does nothing for me.