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In The Last Day

Article: Nikon Lens Names & Acronyms Explained

Posted 10/7/08 by Steve Denton
Last Updated: 12/31/69
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 This article is part of the following Gear Guide(s): 

One of Nikons current best selling lenses, is the AF-S DX VR Zoom-NIKKOR 18-200mm f3.5-5.6G IF-ED, perhaps not the easiest name to remember. However, the name does give a very good description of the lens. This section will outline what all those acronyms, and other terms found in lens names and descriptions, actually mean.

These are the terms typically used to describe a lens, a full descriptions of each term follows:

XXmm | XX-XXXmm | Zoom | NIKKOR | DX | FX | IX | UW | VR | ED | ASP | IF | RF | fX.X | fX.X-X.X | G | D | CPU | AI-P or P | AF-S | AF-I | AF | AF-N | SWM | Pre-AI, Non-AI or NAI | AI | AI'd | AI-S | N | SIC or NSIC | NIC | C | Micro | PC or PC-E | Reflex | UV | Bellows | Medical | Noct | Fisheye | OP | U, B, T, Q, P, H, S, O, N, D | Auto | E | CRC | DC | GN | Series E

The Basics:

XXmm: This is the focal length of the lens, for example 85mm. If there is just one number (as opposed to xx-xxmm), then this is a prime lens, meaning it has a fixed focal length (and therefore cannot zoom). On a Full Frame, or FX camera, a 50mm lens gives approximately the same perspective as the human eye, so anything longer than 50mm (for example 200mm) is referred to as a telephoto lens, and will make objects appear closer through the viewfinder. Numbers shorter than 50mm are referred to as wide angles, and make objects appear farther away. For DX cameras, 35mm gives approximately the same perspective as the human eye.

XX-XXXmm: This denotes a lens with a variable focal length, also known as a zoom lens, and allows you to zoom in or zoom out so you can better compose the photograph without having to move closer or further away to get the picture you want.

Zoom: Denotes a lens with a variable focal length, allowing you to compose the photograph by zooming in or zooming out.

NIKKOR: A name used by Nikon on many of its lenses over the years. First used in 1932, originally used to designate the higher quality optics Nikon produced, but in recent years has been used on almost all Nikon lenses.

Lens Systems:

DX: Introduced in 2003, this is used to designate a lens that's designed to be used with DSLR's containing Nikons DX Sensors, also known as crop sensors. Nikons crop sensors measure approximately 15.8mm x 23.6mm, and are used in most of the current range of Nikon DSLR's, including the D300, D90, D60 and D40. DX lenses can be used on Full Frame cameras (also known as FX cameras) like the D3 and D700, however the image will be cropped. In the case of the D3 and D700, using a DX lens in DX Mode will give a 5.1 megapixel image, instead of the 12.1 megapixel image these cameras usually create. Therefore using a DX lens on an FX camera gives you the middle 42% of the image that you would get with a non-DX lens. If a lens is not marked as DX, then it will work on both FX and DX DSLR's, as well as older film DSLR's.

FX: Introduced in 2007, refers to a full frame sensor (approximately the same size as 35mm film). This term isn't explicitly used to identify Nikon Lenses, however FX is occasionally used to describe a lens that will work with an FX sensor (and 35mm film).

IX: Lenses for the Pronea APS (Advanced Photo System) cameras, will not mount on Nikon DSLR's.

UW: Underwater Lenses for the Nikonos Underwater SLR system.

Common Lens Attributes:

VR: Short for Vibration Reduction, a mechanism to counter camera shake and vibrations, by physically moving a lens or group of lenses to counter motion. VR II is the newer, improved system, but the VR lens designator is often used regardless of whether the lens has VR or VR II.

ED: Short for "Extra Low Dispersion Glass", indicates that one or more softer, more expensive lens element has been used in the lens to help prevent chromatic aberration.

ASP: Indicates a lens that has aspherical elements, which help eliminate chromatic aberration and other potential lens aberrations.

IF: Internal Focus, meaning focusing is achieved by moving internal lens groups, so the front lens element will neither extend or rotate during focusing.

RF: Rear Focus, meaning focusing is achieved by moving the rear element of the lens.

Maximum Aperture:

fX.X: The maximum aperture of the lens. The lower the aperture, the more light the lens can let in. Lenses with low aperture numbers are often called "fast" lenses, because they allow the use of higher shutter speeds or use in lower lighting conditions.

fX.X-X.X: Designates the maximum aperture of a zoom lens who's maximum aperture varies depending on focal length. The first, lower number is the maximum aperture at the zoom lenses shortest focal length, and the higher number is the maximum aperture at the longest focal length.

Camera Body Communication:

G: If used immediately after the f number, this indicates a lens that does not have a manual aperture ring, the aperture can only be controlled electronically by the camera body. This means G lenses will not work with some of the older Nikon film bodies, including all non-autofocus bodies. G lenses support the same features as D lenses (see below).

D: Introduced in 1992 and short for Distance, if used immediately after the f number this indicates a lens that transmits focus distance information to the camera body, allowing it to be used with Nikons 3D Matrix Metering.

CPU: Short for Central Processing Unit, used to designate lenses with electrical contacts in the mount to allow them to communicate with the camera body for metered operation.

AI-P or P: Short for AI with Program, used on early CPU lenses only.


AF-S: Short for Autofocus-Silent, used to designate a lens that uses Nikons SWM (Silent Wave Motor) technology to focus the lens. This it the most modern, fastest, and most accurate focusing system Nikon has produced, and AF-S lenses will autofocus with all current Nikon DSLR's. AF-S lenses were introduced in 1996.

AF-I: Autofocus-Internal, used briefly between 1992 and 1996, mainly on longer telephoto lenses which used a DC motor in the lens to focus.

AF: The first Nikon autofocus lenses were designated AF, and had a mechanical coupling in the mount to allow the autofocus motor in the camera body itself to focus the lens. Some of the current consumer Nikon DSLR's do not have focusing motors, so cameras like the Nikon D40 require the use of AF-S lenses if autofocus is needed. AF lenses will still mount to the camera, but have to be focused manually.

AF-N: A slightly improved version of AF, used on lenses that had a rubber focusing ring for manual focus, rather than a plastic one.

SWM: Silent Wave Motor, the in-lens motor used to focus the AF-S and AF-I lenses.

Lens Mounts/Metering:

Pre-AI, Non-AI or NAI: This is an unofficial designation used for lenses manufactured prior to 1977, that have a prong fixed to the aperture ring that hooks up with the coupling in the camera to perform metering.

AI: Automatic Indexing, a new coupling system introduced in 1977. AI lenses still have the metering prong found on the older Pre-AI lenses, and also have a ridge and a post on the aperture ring that are used instead to communicate aperture information to the camera – as the aperture ring is turned, the ridge moves a lever in the camera mount.

AI'd: An unofficial designation that is used to refer to lenses that have been (sometimes partially) converted from non-AI to AI.

AI-S: An improvement and replacement on the AI mount, in which the lens aperture moves linearly in relation to its stop-down lever (this is indicated by a special notch in the lens mount), and AI-S lenses with a focal length of 135mm or longer are indicated by a special ridge on the lens mount (which was used by FA, F501, and F4 only).

Lens Coatings:

N: Indicates the lens utilizes Nikons Nano Crystal Coat, represented by an N inside an elongated hexagon on the name plate on the lens.

SIC or NSIC: Nikon Super-integrated Coating, a lens multicoating system used to reduce flare and ghosting.

NIC: Nikon Integrated Coating, a lens coating system used to reduce flare and ghosting.

C: Used on earlier lenses to indicate the lens was coated.

Specialized Lens Features:

Micro: Also known as macro lenses, lenses that allow for high reproduction ratios, typically 1:1, allowing for macro photography.

PC or PC-E: Short for Perspective Control, the lens allows for shift, and often tilt movements, to control perspective and depth of field. Typically the plane in focus is parallel with the sensor in the camera, PC lenses allow you to move this plane of focus so that it is no longer parallel to the sensor, for example if you are standing at the foot of a very tall building and angling the camera upwards, a PC lens would allow you to get all of the front of the building in focus using a shallow depth of field. PC-E lens marking indicates an electromagnetic diaphragm (see E below).

Reflex: Indicates a mirror, or catadioptric lens. Usually used for longer focal lengths, the most famous being the 500mm Reflex. The design used mirrors within the lens to achieve a smaller, lighter, cheaper lens than you could get with a traditional refractive design. Reflex lenses also tend to suffer less with chromatic aberration. The disadvantage however, is that you typically have a fixed aperture lens (500mm f8 for example), the lenses can produce images with lower contrast, the lenses tend to be very wide, and out of focus elements in the image tend to be donut shaped.

UV: Lenses designed for ultraviolet photography.

Bellows: Lenses for macro photography, specifically designed to mount on a bellows unit.

Medical: A macro lens with a built in ring light flash system, designed for clinical/scientific applications.

Noct: Meaning "Night", a fast low light lens designed for maximum sharpness as the widest aperture.

Fisheye: An extreme wide angle lens that distorts the image, making the center of the image look larger and the peripheral areas more compressed.

OP: Short for Orthographic Projection, a fisheye lens that distorts more than a normal fisheye lens.

Other Lens Markings:

U, B, T, Q, P, H, S, O, N, D: On some lenses made prior to 1976, these letters can appear immediately before or after the word Nikkor, and indicate the number of optical elements in the design. The letters are short for Uns (1), Bini (2), Tres (3), Quatour (4), Pente (5), Hex (6), Septem (7), Octo (8), Novem (9), or Decem (10), and can be combined (e.g. BD would indicate 12 elements).

Auto: Used on earlier lenses to indicate the lens has an automatic diaphragm aperture (not autofocus)

E: Indicates the lens had an electromagnetic diaphragm, which can be operated electronically from the camera (older lenses relied on a mechanical linkage).

CRC: Short for Close Range Correction, indicates the lens has been designed for improved focus at close focusing distances, usually found on Micro lenses.

DC: Short for Defocus Control, these lenses have a separate control ring for spherical aberration, which effects bokeh (the appearance of out of focus areas).

GN: Short for Guide Number, to assist with flash exposure on lenses without auto flash metering. The flashes guide number is set on the lens to modify the aperture for correct exposure.

Series E: A lower cost line of lenses made in the 1980's for consumer SLR's, and were branded "Nikon Series E" instead of Nikkor.

Related Articles

For more information on Nikon Lenses:

Nikon Lenses Explained

History of the Nikon F Mount

Nikon DSLR/Lens Compatibility

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