This is why J8s are often shimmed to work with Leica bodies. It is not that hard to do yourself. There are lots of old threads that describe what to do, and tutorials floating around the Internet. With the J8 there are two things going on. There is the particular focus distance that is adjusted to be most accurate, and there is the effect of focus shift. An ideal lens would be 'correct' at infinity, and would then be accurate over the whole focus range. Typically the J8 is shimmed to be most accurate wide open at a short distance, say 1m. Wide open, infinity will be off. When you stop down focus shifts back, and at say 5.6-8 infinity will be accurate. At these apertures depth of field covers the short range accuracy. You end up with a great lens that focussed well in all situations except wide aperture long distance. It's a worthwhile trade off in most situations.
