Nikon offers owners of SLR (single lens reflex) cameras several zoom lenses. Users can turn the zoom ring on these lenses to magnify an image. At the time of publication, zoom lenses range in price from $100 to several thousand dollars depending on the technology they incorporate and their focal length. Options available also depend on the specific camera used.
FX and DX Modes
Nikon currently offers two size censors on the camera body. The FX line uses a 24 mm-by-36 mm censor called a full-frame censor. The DX line has a smaller censor of 15.6 mm-by-23.6 mm. The smaller censor induces a multiplicator factor of 1.5; meaning that a 50 mm lens on a DX body will produce the same image as a 80 mm lens on an FX body. Special lenses were created for the DX system as it allows for smaller and cheaper lenses to be built. However, the DX specific lenses aren't compatible with FX bodies.
AF-S versus AF-D
Nikon started building auto-focus zooms using the AF-D system. That system uses a small motor inside the body to turn a screw in the lens to focus. That system was slow compared to the lens motor used in Canon equipment. Nikon released a newer AF-S system using a motor inside the lens while still retaining the motor in most camera bodies. Nikon started building its new camera body without the motor necessary for the AF-D lenses to function.
VR
Lenses equipped with the Vibration Reduction (VR) ability have a built-in system that reduces the amount of vibration when holding the lens in your hand. As a rule of thumb, a 200 mm lens should only be hand-held at a shutter speed not less than 1/200 of a second to have a sharp image. VR will allow for the same 200 mm lens to be hand-held at 1/50 to 1/25 of a second, depending on what generation VR is used in the lens.
Professional Line
Nikon reserves certain technology for its professional line. The professional line offers users a fixed aperture, meaning that the aperture is constant throughout the zoom range. Most lenses have variable apertures, meaning that a 18-200 lens will have an aperture of F3.5 at 18 mm, and F5.6 at 200 mm. The higher the aperture, the lower the amount of light reaches the censor. The professional line zoom is splash proof, has higher quality optics and doesn't change its length when zooming in to take a photo. However, the lenses are larger and several times more expensive than the regular Nikon line of zooms.
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