Nikon 45mm F2.8 P review
It's a vanity lens, sure, but it's also fun.
Don't buy this lens unless you don't mind spending several hundred dollars just for the fun of it. In terms of value, you can do better:
If you want the look of the 4/3 tessar 45mm, buy a 45mm GN.
If you want the feel of a manual focus pancake, buy the short barrel Ai 50/1.8S or Series E.
If you want a high quality, convenient standard prime lens, buy the 50/1.8G.
The Nikkor 45mm F2.8 P is a modern remix of the 45mm GN. It drops the cumbersome GN coupling, flips the focus rotation back to the normal Nikkor direction, and adds the IC coupling contacts and a sweet screw in lens hood. Released for the FM3a and now discontinued, the lens was never a mass market product and is now more of a collectors item than a practical everyday use optic.
It's not even that easy to use. The focus ring is tuned for speed rather than accuracy, and the small size works against it. The lens is well made, however, so the focus ring is properly damped ... it's certainly not inconvenient, just not as practical as even the 50/1.8 AiS in terms of ergonomics.
Optically it has very much the same look as the 45mm GN, which is to say notable for the high contrast and exceptionally clean transitions. It is neither exceptionally sharp nor exceptionally well corrected, but it is very honest in what it does. What distortion there is pure and uncomplicated - a direct consequence of only having 4 elements no doubt.
This isn't a lens you buy for the bokeh or the low light capability, though with modern FX cameras and their superb high ISO it's more practical today than it was in the film or early dSLR days. The OOF rendering can be nervous, but never nasty. As you can see in the second example below, stopped down and focused close, the background blur is very pleasant.
AiP means the lens can meter in M mode, and work in PAS modes also. For some reason it consistently underexposed by about 1 stop on my D750. No big deal, but curious.