28/2.8 AIS focuses down to .8 meters, IIRC.

Re: the Series E lenses, some were duds for still photography, some were great. 75-150, the aforementioned 100, etc...

Differences between pre-AI, AI'd, AI, and AIS:

Pre-AI: Aperture ring extends down over the lens mount all the way around and will usually interfere with the AI coupling tab on those cameras that do not have a flip-up tab. Sometimes you might get lucky, but not worth it. Certain pre-AI lenses will also damage an F4, FG, or FA if mounted, even after AI conversion. Rear element baffle comes in contact with the lens speed sensing cam inside the mirror box and can break it off. Notably all pre-AI 28/3.5's, all 55/1.2's that have a serial below 400001, and late pre-AI 35/1.4's. Prongs are solid and are either triangular or rounded.

AI'd: A pre-AI lens that has been converted, either by using the factory AI kit or by milling the aperture ring. Frequently, eBay sellers, KEH, and other camera shops will mistake a factory AI'd lens for an AI lens. Said lenses do not have the lens speed sensing tab that the factory AI lenses have, and, if they're the lenses mentioned above, will still damage the F4, FG, and FA bodies. Not sure about the N2000 or N2020, but I suspect they also would have an issue with it, since they are essentially motor driven FG's. Best to buy an actual AI lens, if you're going to be using one of those lenses on an F4 or other similarly equipped camera. Factory AI'd lenses frequently have an AI style prong, unless I get my hands on them. At that point, they typically get reverted to the stock pre-AI prong.

AI: Lenses typically look identical to the K-version pre-AI lenses, except for the AI aperture ring, the addition of the lens speed sensing tab on the rear element baffle, and, a lighter gray rubber focusing ring grip. Both the 35/1.4 and 105/2.5 have a more limited aperture range than the pre-AI versions. Prong now has two semicircular holes and the center notch is cut all the way down to the mounting plate. Prong became thinner later in production. Most AI lenses had 5 screws on the mount until about 1978-79, when a lot of the lenses went to a 3 screw mount.

AIS: Shorter focusing throw, addition of the lens mount scoop used for the FG and FA bodies to tell them to prefer wider apertures and faster shutter speeds in Program modes with 135mm or longer lenses, minimum aperture is now orange. Lenses are typically smaller and lighter than the AI counterparts. All Series E lenses are AIS, as are AF and AF-D Nikkors, as well as AF-I and AF-S Nikkors with aperture rings. Some AIS lenses didn't have prongs (50/1.8 AIS pancake, 35-70/3.5-4.8, all Series E). Most lens formulations remained the same. The 28/2.8 being an exception, of course. 300/4.5 AIS lenses have f/32, instead of f/22 as minimum aperture on both non-ED and EDIF versions. Tripod mounts were also redesigned.

AI-P: AIS lens with a CPU chip. 45/2.8, 500/4, and 1200-1700 zoom are the only ones I'm aware of. None have prongs on them.

-J