Only thing I can add to the info Tiffany quoted regarding focus stacked images, is that my own old school camera, did not allow for automatic focus shifts for the purpose of focus stacking, nor would automatic focusing work at all, at these higher magnification. So focus is all manual and the whole camera rig is moved very slightly to produce different focused slices that later can be combined in the computer. Handheld this is a bit of a hit and miss, so it is always better to try to get at least some 'normal' photos and see any focus stacks as a bonus.
