Three Japanese optical companies merged in 1917 to form "Nippon Kogaku K. K.," the company we now call Nikon. The new company began to manufacture optical glass in 1918, and made glass elements for binoculars and microscopes. By 1932, the company adopted the trade name "Nikkor" for its camera lenses, and by the end of WWII production included cameras, microscopes, binoculars, surveying instruments, measuring instruments and ophthalmic lenses.
Nikon introduced the "D" series of lenses in 1992 and the "G" lens in 2000. There are few differences, but they are critical.
The D Lens
The "D" designation on Nikon lenses stands for "Distance Information," and is a technology in the lens intended to help the exposure meter by "telling" the camera the distance at which the lens is focused.
In normal lighting conditions the feature means very little, as the meter has less work to do and will produce reasonably proper exposures. If the subject is backlit and you use a flash to illuminate the foreground subject, however, and the camera is focused other than on that subject, the resulting image will be too light. You may get a different weird result if you focus the camera on the foreground subject and use the flash, because the backlit background will be overexposed.
These aberrations caused more problems with film cameras than with newer DSLRs, because the newer technologies accommodate many more variables.
You'll commonly see the D lenses marked "AF-D," where "AF" simply means Auto Focus. Older "straight D" lenses will work just fine, but you have to focus manually by turning the focus ring on the barrel.
Older AF-D lenses focused more slowly than newer ones, but that difference comes from mechanics inside the lens, not from anything that relates to the D feature.
The G Lens
Introduced in 2000, the Nikkor G series lenses do not have an aperture ring, therefore will not work on manual focus cameras, which would have every image shot at the smallest aperture that particular lens has.
The G series lenses also have more plastic, including the mount. Some camera enthusiasts prefer the more rugged metal mounts, since a lot of lenses get tossed around in camera bags, often without caps on either end. A cracked or chipped mount can result in a light leak, which will ruin the images, whether film or digital.
All G lenses are D in terms of internal structure and the number of elements. The G lens may weigh slightly less because of the substitution of plastic for metal.
G lenses also come in AF-G models, and of course are far better suited to the newer Auto Focus camera bodies.
The G series lenses came to market at lower costs than their D brethren, sometimes at the sacrifice of features that create incompatibilities with older camera bodies.
Which Nikkor Lenses Have D or G Designations?
Nikon, in its Nikkor lens lineup, makes hundreds of lenses, both prime (one fixed focal length, for instance, 50mm) and telephoto (18-200mm, for example). The feature list includes F, AI, E, AI-s, AF, AI-P, AF-n, AF-D, AF-I, AF-S, G, PC-E, ED and a few other designations found only on medical telescopes and other high-end optics. Any glossary of camera and lens terminologies will explain what those designations mean.
What Do D or G Lenses Cost?
Nikkor lenses are state-of-the-art pieces, many of which have extremely specialized uses, such as macrophotography. Costs can vary from vendor to vendor, and you may find new lenses on such auction sites as eBay. Laying out a comprehensive cost chart for the Nikkor family of lenses would result in a huge display that won't help you. As of 2009, you can pay less than $100 for a relatively "standard" focal length prime lens (50mm), or more than $5,000 for a specialty telephoto lens with a large (e.g., 1:1.2) aperture.
Final Considerations
You'll base decisions about D or G lenses on your needs as they're influenced by the camera body or bodies you have. Nikon is very good about backward compatibility, so with very few exceptions, newer lenses will mount and work fine with older camera bodies, though you may lose some automatic features and have to make decisions about lighting, shutter speed or aperture settings. For example, you may need a light meter because an older lens introduced during the film era may get fooled by the better technologies in digital bodies.
Tags: series lenses, camera bodies, Auto Focus, decisions about, focal length, foreground subject, lenses also