Oops, I seem to have accidentally deleted my post so I'll try again.
I have a couple of lenses that have benefited from fine tuning, and as an experiment I tried several methods on both. On the 16-85DX, which back focuses, I found that a tape on the floor, a carefully placed target, a moiré pattern, and dot tuning all worked, and all agreed pretty well. I can't remember now which result I used finally but it might have been the dot tune.
But for the other lens, a 50/1.4D, the dot tune method was useless. Tape, target and moiré all worked pretty well, and the final result of -9 makes a huge difference in a lens that was long a disappointing dog. But for some reason, although the lens focuses with reasonable consistency, the dot stayed lit through nearly all the adjustment range. As I recall, it was lit from about +16 all the way to -20. That shows a back focusing bias, but clearly one cannot center that reading to the correct -9.
I experimented with a couple of lenses that appear not to need any fine tuning, and the dot method appeared to confirm that, with the center point being at or near enough to 0.
In my experiments, I found dot tuning to be accurate if the dot goes out before it hits either extreme, and it's the method I'd use first just because it's so simple and needs no equipment, but if you can't center it, either because the dot itself is too sloppy, or because the tuning amount is too near to the edge, some other method will have to do.
p.s. the camera in this case is a D7100 that otherwise seems to be well tuned and needs no adjustment for most lenses.
