Making Sense of Lens Acronyms

I'm overdue in writing this article. While Nikon has stuck with the F-mount for over 30 years now, they've made plenty of additions and tweaks over the years, and it seems that every time they do, there's a new acronym to learn. First, a little history, then the translation dictionary (right column).

The original F-mount appeared in 1959, and lenses that were produced from then until about 1979 are usually referred to as Pre-AI. These lenses are dangerous on current Nikon bodies. With the exception of a modified F5 and the D40/D40x, mounting one of these lenses on your new Nikon will result in damage, so don't even try it. If you find that you have one of these lenses and want to use it on a current camera, you must have the lens converted to AI first. Nikon used to do this, but now it's done by a number of independent companies.

In 1977 Nikon added a feature called Aperture Indexing (AI). By about 1979, most Nikkor lenses were being produced with AI. Any AI or later lens will mount on all current Nikon bodies. Most bodies, however, will not meter with such lenses, as they don't have the mechanical indexing parts to get maximum aperture information from the lens. Exceptions are the F100, F5, D1 series, and D2 series, each of which have slightly different metering compatibilities with these lenses (see chart, below).

Nikon kept adding new variants of AI: E in 1979, AI-S in 1982, and AI-P in 1988. They are essentially the same to a current camera body as AI lenses, with the exception of AI-P, as it is has a CPU built into it (see next paragraph). You can add a chip to any AI or AI-S lens to effectively make it an AI-P lens. I used to recommend a third party service to do this, but judging from the complaints I've received about it in the past year, I've elected to remove mention of it. At this point, you'd need to be relatively good at finesse work and order the required parts directly from Nikon, then install them yourself.

The first autofocus lenses appeared in 1986. These have a "CPU" built into the lens, but this really is just a fancy way of saying it has an electronic transfer of basic lens information to the camera. Since then, we've had several variations of autofocus lenses: D-type (1992) adds distance information to the data supplied by the lens to the camera, AF-I, AF-S add in-lens focusing motors, and G-type removes the aperture ring (but is otherwise identical to D-type). The main things to watch for are non-D, D, or G. This is found by looking at the aperture designation on the barrel, which would be something like f/2.8, f/2.8D, or f/2.8G for plain autofocus, D-type, and G-type respectively.

(Nikon also made lenses with the type of IX. These lenses were designed for the Pronea series of cameras, which use the Advanced Photo System format film. They cannot be used on 35mm film or digital bodies, so just ignore them unless you have a Nikon Pronea.)

In terms of functionality, we're ready to get more specific now (I'm just going to cover bodies from the FM2n/F4 era onwards here):

Mounts = can be mounted on the camera in question
Meters = all metering functions work with the lens in question
No matrix = matrix metering is disabled with the lens in question
3D metering = distance taken into account in matrix metering
Advanced flash metering = some advanced balanced fill-flash mode(s) supported

*Special note: Since some Nikon cameras only focus with AF-S and AF-I lenses, other manufacturers have now started imitating those lenses. This page is focused on Nikon's designations, but to be complete I should mention that Sigma's HSM and Tamron's NII designations are essentially the same as Nikon's AF-S designation.

In shorthand: on most recent Nikon bodies, you want an D-type or G-type lens to get the most metering and flash capability; any other type of lens compromises something in the metering or flash system slightly. On a few cameras (D40, D40x, D60, and D5000) only AF-S (or AF-I, HSM, NII) lenses give full compatibility.

But Nikon's acronyms don't stop with overall lens type; plenty of sub-categorization exists. So check out the column to the right to find out what the acronym you're looking at means. If you encounter a term I haven't defined, let me know so I can add it to the list.

Finally, even Nikon lens hoods have meaningful acronyms. The letters in the name of the hood specifies something about the hood itself:

Version Info:
2/6/04: Fixed F4/Pre-AI metering
2/23/06: Added Nano Crystal Coating, fixed a few minor typos
3/2/06: Removed recommendation for third party service due to complaints about it
6/8/07: Added D40/D40x, D80, S5 Pro, fixed minor issues
4/2/08: Added D60, D300, D3, corrected F6, added Nano, FX, SWM
6/22/09: Added D5000, minor corrections, added Sigma/Tokina note

AF-S ED-IF G VR N
Achieved: 6/8/2007

Note: with pre-AI lenses Nikon often used a single letter abbreviation to indicate the number of elements in the lens: U (uni) =1, B (bi) =2, T (tri) = 3, Q (quadra) = 4, P (penta)-5, H (hexa) = 6, S (septa) =7, O (octa) = 8, N (nona) = 9, and D (deca) = 10). Usually these letters were appended to Nikkor, as in Nikkor-Q 135/2.8, which would be a pre-AI 135mm f/2.8 lens with four elements (Q). Keep that in mind when deciphering the alphabet soup Nikon has used over the years. If you're dealing with a really old lens, a single letter alongside the Nikkor is likely to refer to elements, not the terms shown below.

A -- The original bayonet lens type (1959). Manual focus lens. Considered Pre-AI

ADR -- Aperture Direct Readout. A fancy way of saying that aperture scale can be seen directly by the cameras that have overhanging prisms (ala F4, F5). Started with AI lenses in 1977.

AF-I -- An autofocus lens with an Integrated, coreless focus motor (1992). All AF-I lenses are D-type, but some older film bodies can't autofocus with them (N60, N8008).

AF-S -- An autofocus lens with a Silent wave, integrated, coreless focus motor (1996). Basically an update to AF-I. Some older bodies can't autofocus with them (N60, N8008). Some newer bodies (D40, D40x) can only autofocus with them.

AI -- Aperture Indexing (1977). Manual focus lens.

AI-P -- An AI lens variant (1988) that was "chipped" to send data to the camera.

AI-S -- A variant of AI designed to be used with Program and Shutter-priority exposure modes (1982). Manual focus lens. Distinguished by smallest aperture being printed in orange and a small scoop on the bayonet flange, which transmits aperture info. Otherwise same as AI.

ASP -- Lens has aspherical elements in its optic design. Aspherical lenses eliminate coma and other types of lens aberrations by using complex curves in the design of lens elements.

C -- A lens coating type (Nikon Integrated Coating) for Pre-AI lenses. Distinguished by a C after the lens designation and a black filter ring.

CRC -- Close Range Correction, means that the lens was designed to provide superior focusing at close distances and with flat fields.

D -- (1992) Adds distance information to the data transmitted to the camera via chip. Distinguished by the D or G after the lens designation.

DC -- Defocus Control lens, allows the photographer to change the degree of spherical aberration in the out-of-focus areas to provide for better bokeh.

DX -- (2003) Indicates a lens designed to cover the smaller image circle of the digital camera bodies. May still work on 35mm bodies at some focal lengths.

E -- A special type of AI lens (1977) introduced with the consumer-oriented EM body. Says Nikon Series E on the lens. Light in weight, plastic in construction, but optically good.

ED -- Extra-low Dispersion element(s) used in the lens.

FX -- (2007) 35mm full frame digital sensor. While Nikon doesn't explicitly use this acronym yet with lenses, it has used it casually to refer to lenses that cover the full 35mm film (and FX digital sensor) frame, as opposed to lenses that cover smaller imaging sizes, such as DX or IX.

G -- Removes the aperture ring from a D-type lens. Thus needs to be used on camera with Command dial control of apertures. With some older cameras (N90s, for example), can be used in Program or Shutter-priority exposure mode, though.

IF -- Lens uses internal focusing rather than moving or turning outer elements.

IX -- Lenses for the Pronea system (Advanced Photo System). Can't be used on the 35mm or digital bodies.

K -- Another Pre-AI lens type, this time with rubber focus rings.

N -- Originally, the actual designation used for the first AI lenses; beginning in 2005 it now stands for Nano Crystal Coat, a special type of flare reduction coating applied to newer lenses.

N (gold emblem)-- Nano coating. A crystalline coating that eliminates internal lens element reflections, reducing ghosting and flare.

NIC -- Nikon Integrated Coating. A fancy way of referring to Nikon's glass coating system, which is used to help reduce flare and ghosting.

PC -- Perspective Control lens, allows the front of the lens to be shifted relative to the rest of the lens to correct for perspective. All PC lenses are either AI or AI-P in type.

RF -- Rear Focusing, means that lens achieves focusing by moving the rear elements; similar to IF.

SIC -- Super Integrated Coating, a multi-layer flare reduction coating, usually applied to the more complex zoom lenses.

SWM -- Silent Wave Motor. This is the motor in the lens used in AF-I and AF-S lenses.

UW -- Underwater lenses, destined for the Nikonos systems.

VR -- Vibration Reduction lens, corrects for camera movement during exposure. VR function only works on post F5 cameras (e.g., not F4, N90s, N60, N70, N8008). Lately, Nikon has been using a VRII designation to indicate some advances to the vibration reduction system.