Nikon Lens Designation Alphabet Soup
If you're new to the Nikon system, or perhaps even if you're not, the endless strings of seemingly random letters that Nikon tacks onto the end of their lens names can seem confusing. Beyond the basic focal length and aperture designations, there's a lot you can learn from what I lovingly call the "Nikon lens alphabet soup."
Most new lenses are autofocus, which Nikon thankfully designates as AF. That's an easy one, but when it comes to non-autofocus lenses it rapidly gets more complicated. The earliest manual focus lenses didn't need extra letters to designate them as such since no other kinds yet existed. Today however they are known as non-AI or pre-AI to distinguish them from the later AI lenses. If you have a lens with a funny metal forked prong (known commonly as "ears") sticking out from one side near the bayonet mount, it may well be a non-AI lens. These ears actually mated with a prong on early camera bodies. To tell for sure if it is non-AI, check the outer black rim around the lens mount. If it's continuous and smooth all the way around, you have a non-AI lens. Today, purchasing non-AI lenses is pretty much limited to lens collectors rather than photographers. In fact, such lenses aren't even compatible with current bodies and can in fact cause damage if used.
The designation AI stands for auto-indexing. These lenses still have ears for backward compatibility but now have an AI ridge on the edge of the lens mount as described above. This made changing lenses far simpler since the camera and lens mated correctly pretty much on their own. AIS lenses are similar but have a scoop shaped groove machined into the bottom of the lens mount to improve the process. Nikon used to offer a service to modify a non-AI lens to add an AI ridge (referred to as being "AI'd"). There are still a few companies out there who can do this if you are in need.
Along about 1986 Nikon introduced AF lenses that featured a CPU chip built into the lens. Computer components are commonplace today, but this was indeed radical back then. Still, other companies were coming out with AF lenses too so Nikon had to compete. In addition to the mechanical couplings that earlier lenses had, AF lenses included a row of small metal bumps that served as electrical contacts on one side of the lens mount rim. Over the years Nikon has added additional electrical signals and it is quite common for new lenses to have more contacts than are utilized by current bodies so Nikon can build a path to the future.
Early AF lenses were designated simply as AF but Nikon later came out with AF-D to pass a distance signal based on how the lens was focused. AF-D was mainly just hype I'm afraid since the signal consisted mainly of just "near" or "far." It wasn't an actual distance measurement in feet or meters or anything. Some macro situations did benefit from the added information though, primarily in terms of flash coverage.
Then came AF-S which offered a huge advantage in that the lens contained a motor to focus much more quickly than earlier AF systems that made use of a mechanical linkage to a focusing motor in the body. The "S" stands for "silent wave" and compared to the earlier gear linage system, it was amazing. Quite a few lenses these days are AF-S but when they came out they were revolutionary. Being able to focus that quickly was cool indeed.
There were and still are a few AI-P lenses that weren't auto-focus but still had CPUs in them. I used to have an excellent 500mm f/4 AI-P and currently own the much newer 85mm macro tilt-shift AI-P. Having a CPU allows them to be compatible with all current Nikon bodies even if you do have to focus them yourself. Don't be confused by the letter "P" in the names of some non-AI lenses which stood for five ("penta"). For a number of years Nikon labeled lenses based on how many elements they contained. "Q" stood for "quadra" (4), "H" for "hexa" (6) and so on. If you are unsure, look for the row of metal bumps on the rim of the mount.
These are the main types of lenses Nikon has produced thus far. Additionally, there are quite a few letters that have been used to describe various features. Here are some of the main ones:
IF — Internal Focusing. An IF lens doesn't grow or shrink when you focus it and the front element doesn't rotate. All of the focusing action happens using elements inside the lens. If you are a fan of polarizers or graduated neutral density filters, you want IF lenses. It can be very annoying to use non-IF lenses with either since you will have to manually rotate the filter back into place every time the focus system messes things up on you.
VR — Vibration Reduction. Nikon will tell you that VR is different than Canon's IS (Image Stabilization) system and they're right technically even though both serve the same purpose. A sophisticated mechanism moves an internal element to compensate (to a degree) for camera shake. Far less useful for people like me who shoot most everything on a tripod, but still a nice feature to have for when you need it.
Micro — Nikon's proprietary trade name for a macro lens. "Micro" and "macro" mean the same thing in Nikon speak.
ED- Extra-low Dispersion glass. As light travels through a curved glass element it naturally creates a rainbow due to the difference in wavelength across the visible spectrum. ED glass counteracts this tendency but the stuff is expensive so Nikon only uses it when they need to. Even when they do, most elements are made of less exotic glass with ED glass used only for certain elements, often small internal ones. ED glass can be a huge advantage for telephoto lenses where problems from dispersion would otherwise be greatly magnified.
DX — Although Nikon has started creating full-frame (FX) bodies, most digital bodies utilize a smaller sensor known as DX format. All lenses create circular images of course, but what makes DX lenses unique is that while their image circle is big enough to cover the size of a DX sensor it isn't big enough to cover the size of an FX sensor (or 35mm film frame) at at least some focal lengths. Physically you can use a DX lens on any body, but you may end up with a circular image in the middle of a black frame if you aren't using a DX body.
PC — Perspective Control. A lens capable of shift or tilt/shift movements. This is an odd choice of name since only shift movements correct for perspective problems such as the appearance of tall buildings leaning over or tree trunks converging. Tilt movements allow you to lean the plane of focus over to better align with a subject to make the most of limited depth of field, typically when shooting macro but not always.
Series "E" — I don't believe "E" is an abbreviation for anything specific, but these were basically cheap AIS lenses created for early consumer camera models. They were good optically but had plastic bodies rather than the metal construction of other lenses of the day.
G — You used to have to manually adjust the lens aperture by rotating a ring near the lens mount. Once Nikon started producing cameras that allowed you to control aperture electronically from the body, aperture rings persisted solely for backward compatibility. Eventually Nikon started releasing "Series G" lenses that lacked aperture rings. In some cases this was done to save manufacturing costs on consumer lenses so G lenses incorrectly earned the reputation of being cheap. The truth is though that even some of the earliest G lenses were truly professional quality. Nikon has stated that one reason they did away with the aperture ring is that there physically wasn't room to fit aperture rings, Silent Wave (AF-S) motors, and Vibration Reduction (VR) components in a lens at the same time. Nowadays G lenses are the norm, but they were quite controversial when introduced. Seems kind of silly now.
N — Nano crystal coating. A high-tech coating used on some newer lenses to cut down on ghosting and flare. This can make a big difference on some lenses when shooting outdoors. The "N" stands out on a lens since it's written inside a special gold medallion. Like P, N is also another one of those letters Nikon used in the early days for how many elements a lens had. Back then N stood for "nona" or 9 elements. Times change though, and letters get reused.
NOCT — Nocturnal. These lenses feature extremely wide maximum aperture and are designed for shooting in very low light.
IX — Physically about the same size as the DX digital format, there once was a film system known as APS or "Advanced Photographic System." Far from being advanced today, the system is completely obsolete. IX was Nikon's name for its APS lens line.
DC — Defocus Control. A lens designed primarily for portraiture that allows you to selectively defocus the image.
This is probably an article I should have written years ago since the subject comes up frequently. Nikon doesn't make it easy, but there are a lot of subtleties they need to convey to accurately describe their extensive line of lenses. This covers the majority of designations Nikon has used but is not complete. Given the long history of Nikon innovation, I doubt any one list could be. Even if it were, Nikon would come out with something new next week. Hopefully this helps for now at least.