Yesterday I reported on the Nikon 45mm f/2.8P and the Voigtlander 90mm f/3.5 APO-Lanthar SL II, two diminutive lenses. All of these lenses fall far short of my wish for Otus-grade f/2.8 prime lenses, but all of them are very good by f/5.6 (the 90/3.5 is excellent wide open).
The Voigtlander 40mm f/2 Ultron SL II “pancake lens” (about $449 for Nikon or Canon) is the smallest lens available for Nikon cameras today, though it’s solid metal construction means that it weighs in at a surprisingly heavy 200 grams. For those that want to travel light and compact, it is well worth considering as an alternative is the discontinued Nikon 45mm f/2.8P.
The Voigtlander Ultron 40mm f/2 SL II is manual focus but an electronic (“chipped”) lens, so it acts just like any Nikon-made lens, supporting 1/3 stop apertures and auto aperture control. Ditto for the Canon version.
I reprocessed a 2012 evaluation for images up to 24 megapixels from f/2 - f/22, along with large crops.