I would like to try fine tuning the focus for a specific lens, but the manual for my D7100 does not give a procedure. I assume I would need to use a tripod with a fast shutter speed and a shutter delay to minimize vibrations while doing this. Then take a picture for each of the fine tune settings (from -20 to +20, 41 pictures total) to see which give the sharpest focus. Is this correct? Does the subject distance matter, i.e. fine tune on a subject at the distance I am most likely to shoot with this lens?