>Using my 18mm at F11, while in AF-S focus mode, I can basically >focus on my shoe (I am 6' 4" tall) by pressing the shutter button >half way down to lock the focus. After that, I simply re-adjust the >camera to frame my desired shot. Because the focus point of my shoe >was approx 4.7' (I would bend down a bit), that is going to be where the camera attempts to focus during my newly framed shot, >regardless of if there is a physical object to focus on or not in > the recomposed image?
>Assuming I am correct (and I could be WAY off), in my picture, >2.35' (hyperfocal of 4.7 - half that distance) to infinity would be >in acceptable focus?
You are correct.
>Another question (again, thank you SO much for your assistance and >clarification) would be, why would I need (or want) to switch the >lens to manual focus after pressing the shutter half way down to >initially lock the focus? I am not understanding and I am sure >there is a reason.
The reason you would switch to manual focus is to keep the camera from refocusing after you recompose your shot. Now if you kept the shutter pressed 1/2 down you would not need to switch it. Using this method you could not take multiple shots. By switching to manual focus, you can take multiple shots and the camera will not refocus. This is the method to use on a tripod and optional method handheld.
>Once I initially lock the focus, if I change to the manual setting >on the lens, it will keep that focus distance for as many shots as >I intend to take?
Yes, you are correct. I use this method all the time and it takes all the focus and what is and is not in focus worry away, allowing me to concentrate on my composition. Try it and see what you think. Nothing is more distracting than to include something close in the foreground of a landscape and have it out of focus. This method will prevent that and allow the foreground object to add interest and depth to your scene.
Jerry Jaynes Great Smoky Mountains of North Carolina