Well, well, well ... I hate to say it, but I think my personal copy of the Z 40mm f/2 is a dud. I can't say if that was the case initially (I doubt it) or has something or everything to do with whatever happened during the repair job it's been to, but it's really unacceptable - and irritating, because whatever I do, I'll end up having to send it back to Nikon again.
I just compared it against the Z 35mm f/1.8 (a sharp lens) and my old(!) Nikon 50mm f/1.4 AF and even older Nikon 50mm f/1.8 AF. The latter two went on the FTZ and had to be focused manually (using magnification).
The Z 35mm f/1.8, predictably, produced an image that was really sharp at the point of focus (using AF) while the Z 40mm f/2 was decidedly murky, with major haloing and a strange orange-y colour cast, but little by the way of loCA - I got similar results in AF and MF with this lens, btw. The old 50mm lenses, crucially, both showed considerably worse loCA, but clearly better central sharpness.
That goes against almost everything I've seen and read about the lens coming from reviewers, even my most trusted ones - with the notable exception of LensTip who said the Z 40mm f/2 wasn't really *better* than the 50mm f/1.8D at least wide open - and that lens has the same optics as my 50mm f/1.8 AF. But my lens is *worse* by an obvious margin, wether focused close or in the distance.
During today's outing, I wasn't able to get a sharp image out of it - the f/2 shots in the middle to far distance were all unusable, and the close-up stuff was all marginal. I noticed that already while out: Sharpness/contrast at the AF point was obviously so bad that the camera showed trouble focusing - something that usually just doesn't happen with primes in daylight. And while I didn't pixel-peep then, but now, on my computer screen, it's blatantly obvious that everything further away than perhaps a meter or so that I tried to focus on is just shimmering, no sharp edges whatsoever; closer stuff is a tiny, tiny bit better, but unsatisfactory as well.
Not good. I'll have Nikon Switzerland try and sort it out - and, depending on the result, I'll either return or swap the lens (or keep it if it's cured - but that may be too much to hope for).
It's most probably a (really) "just" bad sample. I really hate it when that happens (who wouldn't), but also have to say that it's basically a first in more than 35 years I'm a Nikon user. Statistically, it had to happen sooner or later - but it's still disappointing, especially since I had (have!) high hopes for this lens.
M.