DSLR Camera Lenses and Abbreviations

There are a couple of common terms used within photography to describe SLR lenses. These are used across all lenses but these are simple to understand and they relate to performance.

Focal length
24-70mm. A lens which covers an area of 24mm (relatively wide) zooming in to 70mm.

Maximum aperture
eg f/2.8 or f3.5 - 5.6

If a lens has one number then that is the lenses maximum aperture across its entire focal range (lower numbers have larger apertures and are faster, shorter depth of field but are far more expensive). If a lens has two numbers then the first one eg f/3.5 is its maximum aperture at its widest and the smaller number is its maximum aperture at its longest.

AF/MF. Switch between Auto Focus and Manual Focus

Canon produce an extremely wide range of lenses for their EOS cameras. This married with the ranges produced by Sigma, Tamron and Tokina gives Canon owners an enormous range of Canon Fit SLR Lenses. The abbreviations used by Canon are as below.

EF: Electronic Focus. Lens mount fitting the entire Canon DSLR system.

EF-S : As above but only working (fitting) on a Canon's APS-C sized digital SLRs such as the 20D, 30D, 40D, 50D and 300D, 350D, 400D, 450D, 500D. The S stands for "short back focus," meaning that the back of the lens is much closer to the CMOS (CCD if you like) than with EF lenses.

USM : USM is Ultrasonic autofocus motors. There are two types is USM micro-USM which is a direct replacement for the systems on older FD motors and the faster 'Ring USM' with manual focus overide.

DO: Diffractive optics. An expensive technology which allows Canon to produce lenses with long focal lengths without the lens becoming much physically longer.

TS-E : Tilt-shift lens, often used for architectural photography to alter the perspective of converging lines and depth of field. Similar to using an old style 'Sinar' camera.

L Lenses : Canon's professional lenses. Refers to their optical quality not necessarily anything specificaly functional. Usually white in colour.

MP-E : Macro Photo Electronic. Lenses designed for macro work through the use of an electronic aperture control function.

IS : Image Stabilisation, A system designed to reduce shake. Nikon have their own version called VR (Vibration Reduction) and Sigma use the term OS (Optical Stabilisation).

Like Canon, Nikon produce a significant range of lenses with their own abbreviations (as below). Sigma, Tamron and Tokina also make Nikon Fit SLR Lenses making the selection almost equally as wide AF DC_ Nikkor Lenses : Defocus-image Control that adjusts the spherical aberration and therefore the blur giving rounded defocussing effect often used in portraiture.

CRC (Close-Range Correction) : Used in fisheye, wide-angle, Micro, and limited medium telephoto, offering high quality at closer focusing distances.

DX Nikkor : As with Canon EF-S lenses, DX lenses are optimised for cameras with smaller sensors. They will fit on other cameras but this is not recommended.

ED: Extra-low Dispersion glass. Gives superior sharpness and optimal colour by correcting th diferences between the angles that blue and red light travel in as they pass through the lens.

IF : Internal Focusing. the focussing mechanisms are within the lens ensuring the lens remains the same size as focal length is changed.

Macro : Lens designed to capture subjects closer to the lens.

G : No aperture ring. Aperture is adjusted electronically by the camera body.

Nano Crystal Coat : non-reflective coating for clearer images with increased detail by reducing reflection from inside the lens.

VR: Vibration Reduction : Nikon's version of Canons IS system, designed to cut down on the effects of hand shake.

PC-E: Perspective Control similar to Canon's Tilt and Shift Lenses.

RF: Rear Focusing. Uses the rear group of lens elements to focus giving faster and smoother AF.

Silent Wave Motor : Silent Auto focussing (as Canons USM)

EX : Sigma's professional lenses offering their highest optical quality.

DG : Like Canons EF lenses, DG lenses can be used with full frame and cropped sensor cameras. They have more coatings to reduce reflection.

DC: Stands for Digital Crop and can only be used with cropped sensor cameras. They are lighter and often less expensive.

ASP: Aspherical lens. Smaller than normal lenses.

APO: Apochromatic lens. Using low dispersion glass limit chromatic aberration.

OS: Optical Stabilisation. As Canon IS or Nikon VR lenses.

HSM: Hypersonic Motor. As Canon's USM system.

RF: Rear focus. The rear elements are moved for quieter and faster focusing.

IF: Inner focus lenses move the middle lens elements, ensuring the lens remains the same length throughout its focal range. This is useful on longer shots as it reduces hand shake.

DF: Dual focus. Does not rotate while autofocusing.

Conv: Can be used with Sigma teleconverters.

ASL : Aspherical Glass.

AD : Anomalous Dispersion. Reduces chromatic aberration..

Di : As Sigma DG.

Di II : Made for APS-C sized sensor cameras (as Canons EF-S).

IF : Internal focus. Lens stays the smae length reducing hand shake at longer telephoto lengths

LD : Low Dispersion Glass to reduce chromatic abberation

Macro : Designed to focus on closer subjects

SP : Super Performance. Tamron's best lens range.

XR : Extra Refractive Glass for improved optical results.

VC: Vibration Control as Canon's IS, Sigma's OS and Nikon's VR