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27-09-09, 03:30 PM
Join Date: Jul 2009
As far as I understand it the idea of focussing about a third of the way into a scene is to approximate the hyperfocal distance. Given that the actual hyperfocal distance is based on aperture, focal length and sensor size, it's usually easier to guesstimate it - hence focussing a third of the way into the scene.
With regards to your specific example, f/11 is a relatively large aperture for generating lots of DoF so you are exaggerating the effect somewhat.
For example (and my apologies for doing this in metric rather than imperial but I've tried to stick to roughly the same figures you've used) with a 1.5x crop sensor and a lens at 24mm, f/11 focusing on a subject 2.74m (9') you get the following:
Near limit: 134.5cm (~4' 4")
Far limit: Infinity
from about 4 and a half foot to infinity should be in "acceptable" focus.
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