Monday, January 24, 2011

Making Sense of Lens

As I get used to the joys of shooting with a DSLR - and the discomfort of lugging it around - it has dawned on me that I know almost nothing about the lens because the kit box comes with a manual only for the body - not for the lens!

The kit-lens that came with the D90 is called AF-S DX NIKKOR 18-105mm f/3.5-5.6G ED VR . Now, what is this hieroglyphic supposed to mean?

Here is what is revealed by the breaking up the code, with some generous help from the gurus on the web -

AF-S: `Auto Focus - Silent` - a "silent wave" focusing lens with an improved focusing speed.  This was achieved by putting a silent wave focusing motor in the lens itself to make it quiet.

DX: 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.

NIKKOR: Brand-name for lenses manufactured by Nikon

18-105mm: Aperture range

f/3.5-5.6: Focal lengths

G: Indicates that the lens does not have a built-in aperture ring (as in D-type lens) and needs to be used on camera with Command dial control of apertures.
Interestingly, G stands for `Gelded`, or castrated! So its not a feature but a handicap! Details can be seen  here.

ED: Extra-low Dispersion elements used in the lens

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).

This lens configuration - called the `standard zoom` (5.8x) -  is supposed to have 15 elements in 11 groups, of which one each aspherical and another one with extra-low (ED) dispersion. Aspherical lenses help in correcting the distortion caused by the wide-angle lenses while the ED prevents dispersion of colors as the pass through the prism and glass elements

Strangely, Nikon sells this kit-lens with a worldwide warranty, but, for the body, it is limited to Japan only.

Codes awaiting translation: vignetting, 'softish corners', barrel distortion,MTF curves,


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