One of my fans/friends on facebook sent me this recently “Nikon sells a ’18-200mm f/3.5-5.6G AF-S ED VR II DX Nikkor Telephoto Zoom Lens.’ I’m a pretty serious amateur who is honestly more into the science than the art of photography and even I’m not 100% sure what all that really means after the focal length and f-stops. A blog explaining lens terminology would be a good read.” I’m sure he’s not alone in his confusion as to what all the numbers and letters in their various combinations means when looking at a lens model, so here you go.
My disclaimer: I’m only truly familiar with Nikon (Nikkor) lenses, so I can’t explain what the same numbers mean in Canon, Pentax, and other company’s lenses, but I’d expect they’d be similar, as they (Lens manufacture’s try to confuse the public any more than they have to, or so they say.)
The Lens model I’ve selected for this “breakdown” is my most often used landscape lens, my (this is what I would say in person) Nikon 17-35mm wide angle lens. Now, onto how the lens would be listed on Nikon’s website or at B & H, or other online retailers, or at your local camera store.

Wide angle photo
Here’s how the lens model reads on Nikon’s website:
AF-S Zoom-Nikkor 17-35mm f/2.8D IF-ED
I’ll break down each portion of the lens model name and then I’ll tell you what it all means, in as plain-as-possible English.
AF-S — Autofocus-Silent. This lens uses a “Silent Wave Motor”, so named by Nikon.
Zoom – This lens is capable of adjusting its focal length using a zoom ring.
Nikkor - This is the brand of lenses produced by Nikon Corporation, including camera lenses for the Nikon F-mount (DSLR and SLR camera bodies).
17-35mm - This lens is capable of adjusting its focal length (zooming) using its zoom ring from 17 millimeters to 35 millimeters.
f/2.8 - This is the maximum aperture of the lens. Since this is a low number, 2.8 compared to 5 for example, this is a “Fast” lens. Lens speed refers to the maximum aperture diameter, or minimum f-number, of a lens. A lens with a larger maximum aperture (that is, a smaller minimum f-number) is a fast lens because it delivers more light intensity (illuminance) to the focal plane, allowing a faster shutter speed. A smaller maximum aperture (larger minimum f-number) is “slow” because it delivers less light intensity and requires a slower shutter speed. Lens speed is important in taking pictures in dim light, and is a key variable in combination with other variables such as focal length and camera format size.
D – This is a lens with “D” functionality. When “D” is indicated after the f-number in the name, the lens electronically communicates focus distance information, which is incorporated into the camera’s exposure calculations in 3D Matrix Metering mode, and also D-TTL and I-TTL flash auto-exposure. All AF-I, AF-S, and G-type lenses are also D-type.
IF-ED – This lens has Internal Focus (IF) and “Extra-low Dispersion” (ED) glass. With internal focusing, focusing is accomplished through the movement of internal lens groups, eliminating extension and rotation of the front lens element, allowing focus to be driven quickly by a small motor. IF lenses allow the use of a polarizing filter without the need to readjust it after focus. Extra-low Dispersion glass is incorporated into the lens to reduce chromatic aberration. Lenses using ED elements usually carry a gold ring around the barrel to indicate that the lens incorporates ED glass.
So, my AF-S Zoom-Nikkor 17-35mm f/2.8D IF-ED, is a autofocus zoom lens with a silent-wave motor, that has a maximum aperture of f/2.8 and a zoom range of 17-35mm and includes internal focusing and ED glass, made by Nikkor. If you ran into a fellow photographer (me for example) and asked them “Hey, what lens are you using?”, they’d probably reply with something like “a fast, wide-angle zoom by Nikon (or Nikkor).” They’d say something like “a 17-35″.

Nikon 70-200mm f/2.8
In addition to the above, you will often see “VR” or “VR II” on Nikon telephoto lenses, such at their AF-S Nikkor 70-200mm f/2.8G ED VR II Lens. For these lenses:
VR - Vibration Reduction Image Stabilization. Vibration Reduction, engineered specifically for each VR NIKKOR lens, enables handheld shooting at up to 4 shutter speeds slower than would otherwise be possible, assuring dramatically sharper still images and video capture.
II - This is a VR lens with Nikon’s second generation of Image stabilization.
So there you have it! If you’re shooting Nikon, that should be fairly complete. If you’re not shooting Nikon, you probably can still get a pretty good idea as to the lens(es) you may have or may be interested in buying.
As always, please ask me any questions you may have.
Happy Shooting!!
Jeff