18/05/2007 by paul
This extract is taken from an article located on Nikon's own website and explains the various abbreviations used on their lenses:
ED: Extra-Low Dispersion glass
High-quality glass that corrects for chromatic aberration, a type of image and color distortion that occurs when light rays of varying wavelengths pass through optical glass and don't converge or focus at the same point. Nikkor lenses with ED glass deliver superior sharpness and contrast, even at maximum aperture. Super ED glass is a new type that is used together with ED glass in some lenses to achieve an even higher degree of freedom from chromatic aberration.
D: Distance
D-type AF-Nikkor lenses relay subject-to-camera distance information to Nikon SLR cameras that feature 3D Color Matrix Metering, 3D Matrix Metering, and 3D Multi-Sensor Balanced Fill-Flash.
G: The lens has no aperture control ring and is designed to be used with cameras that allow setting the aperture from the camera body. G lenses also provide Distance information to the camera.
AI-P: A manual-focus Nikkor lens with a built-in CPU which transfers data from the lens to the camera's metering systems.
IF: Internal Focus
Focus is accomplished without the lens barrel rotating or changing length, an advantage when using a position-sensitive filter such as a polarizer or split neutral-density.
AF-S: Autofocus Silent
Focusing is driven by a "Silent Wave" motor in the lens instead of the focus drive motor in the camera. AF-S lenses focus faster than standard AF-Nikkors and almost completely silently. AF-S lenses with a "II" designation weigh less and are generally smaller than their equivalent predecessors.
DC: Defocus Control
A lens which allows the photographer to control the degree of spherical aberration in the foreground or background by rotating the lens' DC ring. This will create a rounded out-of-focus blur that is ideal for portrait photography. With the DC control set at zero, a DC-Nikkor lens operates in the same way as a non-DC lens with the same focal length and maximum aperture.
CRC: Close Range Correction
Improves image quality at close focusing distances. The lens elements are configured in a "floating element" design wherein each lens group moves independently to achieve focusing. This ensures superior lens performance even when shooting at close distances.
PC: Perspective Control
A lens whose axis can be shifted laterally relative to the film plane, allowing the camera to be repositioned to reduce the convergence of vertical lines in architectural photography.
ASP: Aspherical lens elements
Aspherical lenses minimize coma and other types of lens aberrations, even when used at the widest aperture. They are particularly useful in correcting distortion in wide-angle lenses and help contribute to a lighter, more compact design by reducing the number of standard (spherical) elements necessary.
RF: Rear Focusing
A focusing system in which only the rear lens group moves to achieve focus. This design technique makes autofocusing operation smoother and faster.
VR: Vibration Reduction
An optical innovation that minimizes image blur caused by camera shake and offers the equivalent of shooting at a shutter speed three stops faster, allowing sharper handheld pictures with longer lenses. The system even automatically detects when a photographer pans while photographing a moving subject. VR operation is available only with specific Nikon cameras.
M/A: A focusing mode on some AF-Nikkor lenses which allows switching from automatic to manual focusing with virtually no lag time by simply turning the focusing ring on the lens.
AI: Automatic Indexing
AI became standard on Nikon cameras and Nikkor lenses in 1977. Non-AI lenses coupled to the camera's meter through a system that required a pin on the camera to be mated to a slotted prong on the lens before the lens was mounted, then the aperture ring on the lens had to be turned from one extreme to the other to index the meter to the maximum aperture
of the lens. AI eliminates this entire procedure because meter coupling and indexing occur automatically when the lens is mounted on the camera. Most AI lenses made until a few years ago were also supplied with the coupling prong so they would be compatible with either metering system.
AI-S: Automatic Indexing (modified)
AI-S coupling is a refinement of AI and became standard in 1982. The diaphragm action in an AI-S lens is compatible with Nikon cameras that allow the aperture to be controlled from the camera, as is required for programmed and shutter-priority automatic exposure control. All AF-Nikkor lenses, as well as most manual-focus Nikkor lenses made since 1982, are AI-S.
DX: The lens is specifically designed for use on Nikon digital SLR cameras. It produces a smaller image circle for more efficient coverage of the imaging sensor in these cameras, which is smaller than the 35mm film frame.
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