Interestingly, the stoichiometric ratio (ideal) for diesels is 14.5:1 and I have seen smoke before that mixture (leaner or less fuel) so black smoke is not necessarily unburned fuel, a light haze means you are actually burning at perfect efficiency
But wait... that's under ideal conditions, with perfect mixing. A diesel(at least ours) is a striated charge compression ignition engine. Which means that you are shoving a bunch of fuel in in one spot(so that spot is extremely rich), vs the rest of the cylinder. Depending on how well that diesel gets sprayed/distributed, you will get rich and lean spots.
IDIs are... OK at distributing the diesel; poor because of the injector, but good in that the fuel gets sprayed against a hot precup and evaporated(at least with a warm engine) and then swirled into the rest of the cylinder.
This is also why more modern common rail engines are more efficient - finer diesel droplets = more consistent burning and less rich/lean spots.
More than likely, if you run a more 'dirty' injector like a Stage 1, you would have to run a leaner ratio before smoking. A 'cleaner' injector like a stock one with a higher than stock pop pressure would let you run 'richer' before smoking, due to better dispersion.
Personally, I don't really care - run it a bit lean and just shove in enough air that you can run it "lean" and still make a ton of power.