The 50/2 H (all versions, including the AI 50/2 - they're all the same basic lens, just a different barrel with longer throw helix on the rubber focus ring versions). I have a regular AF 50/1.8 (non-D, Japanese build), which is also a decent lens, but I do think the older 50/2 beats it. Alas, my current 50/2 H is still pre-AI, so it's only used on the FTn, FT2, and the F. I also have the two better non-AF 50/1.4's. The original S version with factory AI ring, and the AI version. For some reason, the SC and the big K versions tend to have a milky green cast, especially with Fuji film, which isn't there with the older S, nor the compact K version or the AI version.