Question about DOF/aperture
But while I'm doing this, do I have to be aware of anything other than what parts are in focus when I'm going to this higher f/number? (I know that the camera will have to adjust the shutter speed for the available light etc.)
If you stop down the lens a lot — say f/16 or a larger number, although it depends on a lot of things — then you risk diffraction in your image, which means that everything will be fuzzier or less sharp. This can be corrected somewhat on the computer with sharpening.
Longer shutter speeds mean that your image might be blurry because of camera shake, but a sturdy tripod or more light should help. Your camera might also raise the ISO sensitivity, giving you more digital noise, particularly in the shadows.
Just exactly where to focus can be somewhat of a problem, and usually you ought to focus on the most interesting point. If you have a whole range of things that ought to be more or less in focus, then focus halfway between them in depth: that is, if you have something 10 feet away, and want it to have the same focus as something 20 feet, then focus at 15 feet. This might be a bit difficult these days since most new lenses don’t have a focus scale.
Another alternative focus point would be at the edge of your subject. Having a sharp outline of a subject often looks better than having a fuzzy outline.