Lenses Explained
Lens Designations - General
28 - 70mm — this is the range of focal lengths covered by the lens, 28mm at the wide end and 70mm at the long end (in this example).
f/3.5-5.6 — this is the range of the maximum aperture of the lens, in this example f/3.5 at the lens’ wide angle setting, changing to f/5.6 at its longest focal length.
A prime or zoom lens with a fixed maximum aperture will have just a single F stop shown in the name.
Lens Designations - Canon
EF — This refers to Canon’s electronic lens mount, used in all Canon camera since 1987. The previous mechanical lens mount carried the letters FD.
L — Canon’s designation for their top-of-the-line lenses is the letter L. These lenses are the best that the company knows how to make at any given focal length and aperture, professional quality, heavy, and the highest priced.
DO — stands for Diffractive Optic and is used on Canon lenses which utilize a unique diffraction grating to control chromatic aberration and reduce lens size and weight.
IS — indicates that the lens utilizes Image Stabilization, which reduces vibration as much as 3 stops, allowing hand holding of long lenses at much lower shutter speeds than would otherwise be possible.
USM — stands for Ultrasonic Motor, a technology that uses sound waves to position the lens elements when focusing. This reduces size, weight and power consumption of the autofocus mechanism as well as increasing speed and allowing for manual override.
Lens Designations - Nikon
A — The original bayonet lens type (1959). Manual focus lens. Considered Pre-AI
ADR — Aperture Direct Readout. A fancy way of saying that aperture scale can be seen directly by the cameras that have overhanding prisms (ala F4, F5). Started with AI lenses in 1977.
AF-I — An autofocus lens with an Integrated, coreless focus motor (1992). All AF-I lenses are D-type, but some older bodies can’t autofocus with them (N60, N8008).
AF-S — An autofocus lens with a Silent wave, integrated, coreless focus motor (1996). Basically an update to AF-I. Some older bodies can’t autofocus with them (N60, N8008). Some newer bodies (D40, D40x) can only autofocus with them.
AI — Aperture Indexing (1977). Manual focus lens.
AI-P — An AI lens variant (1988) that was “chipped” to send data to the camera.
AI-S — A variant of AI designed to be used with Program and Shutter-priority exposure modes (1982). Manual focus lens. Distinguished by smallest aperture being printed in orange and a small scoop on the bayonet flange, which transmits aperture info. Otherwise same as AI.
ASP - Lens has aspherical elements in its optic design.
C - A lens coating type (Nikon Integrated Coating) for Pre-AI lenses. Distinguished by a C after the lens designation and a black filter ring.
CRC - Close Range Correction, means that the lens was designs to provide superior focusing at close distances and with flat fields.
D - (1992) Adds distance information to the data transmitted to the camera via chip. Distinguished by the D or G after the lens designation.
DC - Defocus Control lens, allows the photographer to change the degree of spherical aberration in the out-of-focus areas to provide for better bokeh.
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.
E - A special type of AI lens (1977) introduced with the consumer-oriented EM body. Says Nikon Series E on the lens. Light in weight, plastic in construction, but optically good.
ED - Extra-low Dispersion element(s) used in the lens.
G - Removes the aperture ring from a D-type lens. Thus needs to be used on camera with Command dial control of apertures. With some older cameras (N90s, for example), can be used in Program or Shutter-priority exposure mode, though.
IF - Lens uses internal focusing rather than moving or turning outer elements.
IX - Lenses for the Pronea system (Advanced Photo System). Can’t be used on the 35mm or digital bodies.
K - Another Pre-AI lens type, this time with rubber focus rings.
N - Originally, the actual designation used for the first AI lenses; beginning in 2005 it now stands for Nano Crystal Coat, a special type of flare reduction coating applied to newer lenses.
NIC - Nikon Integrated Coating. A fancy way of referring to Nikon’s glass coating system, which is used to help reduce flare and ghosting.
PC - Perspective Control lens, allows the front of the lens to be shifted relative to the rest of the lens to correct for perspective. All PC lenses are either AI or AI-P in type.
RF - Rear Focusing, means that lens achieves focusing by moving the rear elements; similar to IF.
SIC - Super Integrated Coating, a multi-layer flare reduction coating, usually applied to the more complex zoom lenses.
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). Lately, Nikon has been using a VRII designation to indicate some advances to the vibration reduction system.
Lens Designations - Sigma
APO - Apochromatic lens element(s)
OS - In lens “Optical Stabilization”, analogous to Nikon VR or Canon IS
HSM - “HyperSonic Motor”, in-lens ultrasonic motor, analogous to Nikon AF-S or Canon USM, etc
EX - “Excellence”, professional series.
DG - Coatings optimized for Digital SLRs, still usable on 35mm or full frame
DC - Lenses for DSLRs featuring APS-C size sensors only
DF - “Dual Focus”, lens features clutch to disengage focus ring when in AF mode
HF - “Helical Focusing”, front element of lens does not rotate (for when using circular polarizing filters)
Lens Designations - Tamron
Di - “Digitally Integrated”, featuring coating optimized for digital SLRs, but still usable on 35mm or full frame
Di II - Lenses for DSLRs with APS-C sized sensors only
SP - “Super Performance”, professional lenses
IF - “Internal Focus”
LD - “Low Dispersion” elements
XR - Extra Refractive Index glass
VC - “Vibration Compensation”, in lens stabilization
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