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Lens Specifications Explained

From OCAU Wiki

Back to Photography - Lens Selection


Canon Specific Lens Types and Abbreviations

EF : Lens mount designation for Canon's current camera system. Stands for Electronic Focus.

EF-S : Lens mount designation for Canon's current APS-C digital SLRs (reduced sensor size), for example the 20D, 350D, and 300D models. The S stands for "short back focus," implying that the rear element of the lens is closer to the sensor than with regular EF lenses. EF-S lenses will not mount on Canon film SLRs or Digital SLRs that do not have an EF-S mount.

TS-E : Tilt-shift lens, for control of perspective and depth of field.

MP-E : Macro Photo Electronic. These lenses do not have autofocus, the "electronic" refers to the electronic aperture control. Specialised lenses designed for macro photography.

L Lenses : L refers to Canon's professional range of lenses. Many people take the L to stand for Luxury. Purchases of such lenses can lead to 'L Fever', a condition where all future lense purchases must be L class.

IS : IS refers to Image Stabilisation, Canon's anti-shake feature. Also known as VR (Vibration Reduction - Nikon), OS (Optical Stabilisation - Sigma).

USM : USM refers to the autofocus motor. Ultrasonic Motors (USM) are piezoelectric and offer very fast and silent autofocusing. There are two types: A standard cheaper micro-USM which just replaces the regular electromagnetic AFD motor, and a Ring USM (internal focus) which is much faster and also incorporates fulltime manual focus overide without leaving AF mode (or damaging the focus mechanism).

AFD : An older type of AF motor, AFD (Arc-Form drive) is generally slower and noisier than USM.

DO : Diffractive Optics - DO lenses are found with green rings (as opposed to the red ring around the L-series lenses) to set them apart. DO considerably cuts the size and weight of a lens down while maintaining quality. Still not as sharp as a true L lens but in many cases a viable alternative when size or portability are a concern. How DO works you can read at

A note about the maximum aperture The maximum aperture in a 135mm F/2 lens is (135/2) = 67mm. This means the hole that lets the light in opens up to 67mm. This explains why lenses with larger apertures are more expensive: they require more glass inside larger barrels.

Nikon Specific Lens Types and Abbreviations

G : Electronically controlled aperture (other Nikkor lenses will have an aperture ring allowing physical, manual aperture control useful for the older bodies)

DX : Digital SLR compatible only. Similar to EF-S in Canon land but yet different, as it will work with any DX-format (APS-C 1.5x crop factor) SLR, which includes the entire range of digital Nikon SLRs from the D40 right up to the D2X. While they will still work with a non-DX format camera, Nikon does not recommend it.

ED : Stands for Extra Low Dispersion Glass. It is basically a glass coating that doesn't disperse light as it enters the lens as normal glass does.

D : Lens equipped with a "chip" which allows the camera body to assess the distance of the object being photographed and expose for that object correctly.

IF : Internal focusing - CPU controlled focusing performed by a CPU in the lens itself as opposed to gearing to the lens mount of the camera. The result is a far superior focusing speed.

AF : Auto-focus.

AF-S : Silent-wave auto-focus. Similar to Canon's USM.

VR : Vibration Reduction. Image Stabiliser technology allowing a photographer to shoot three-stops lower than without VR.

Pentax Specific Lens Types and Abbreviations

K : Is the first generation K mount lens, Manual Focus, Manual Exposure. (Listed as Pentax smc)

M : Second generation of K mount lens, smaller then their K counterparts, manual focus manual exposure

A : First Auto exposure lenses from Pentax, manual focus.

F : First generation Auto Focus, Auto exposure lens

FA : Second generation Auto Focus, Auto Exposure lens, On board chip contains lens MTF data for Hyper Program compatible bodies

FA-J : Similar to FA lenses but don’t have an aperture ring.

DA : Digital Lenses, no aperture ring, some have reduced images circle some don’t, Digital coatings and optimised construction.

D-FA : Digital Lenses, aperture ring, covers a 35mm frame. Digital coatings and optimised construction.

* (star) lens : Pentax’s equivalent to Canon’s L, lenses of exception quality. (A, F, FA)

DA* : Pentax’s High spec Digital lenses, Exceptional quality, weather sealed, SDM (Super Sonic Direct drive Motors)

Limited : A prime lens of unparalleled image quality and construction, hand made to the highest quality.

AL : A lens that uses one or more aspherical elements to help improve wide angle performance and sharpness.

ED : A lens that uses extra-low dispersion glass elements reduces chromatic aberrations.

IF : A lens that uses an internal focusing mechanism.

SDM : Super Sonic in lens lens AF motors, silent and accurate Autofocus.

Fixed Rear Element Extension (FREE) : A lens whose last element group remains fixed during focusing.

SMC : Pentax’s lens coating technology.

Quick Shift : Allows manual adjustment of AF after AF lock has been achieved.

PZ : Power Zoom, and Electronic zoom function on KAF-2 mount FA lenses, only functional on Z series FSLRs and K10D digital body.

Information courtesy of Bojidar Dimitrov's Pentax K-Mount Equipment Page

Sigma Specific Lens Types and Abbreviations

EX : An abreviation for the "Excellence" range of lenses. These lenses are similar to Canon's L series, claimed to be superior in build and optical quality to regular lenses. Like the L series they have a distinctive exterior.

DG : A DG lens can be used with both 35mm SLR and digital SLR cameras. DG refers to additional optical coatings that are meant to minimize reflections of light off the sensor itself.

DC : A DC lens is designed so the image circle matches the smaller size of a digital SLR's image sensor compared to a 35mm frame. These are typically lighter than DG lenses but are not suitable for 35mm SLRs.

ASP: An aspherical lens, which is more compact than conventional lenses.

APO: APO or apochromatic lenses are made using a low dispersion glass to reduce chromatic aberration.

OS: Optical Stabiliser. More or less identical to Canon's IS and Nikon's VR.

HSM: "Hypersonic Motor," which in the same way as Canon's USM is used to power the autofocus mechanism and is generally quieter and faster than conventional electromagnetic motors.

RF: Rear focus lenses move the rear lens elements delivering faster, more quiet focusing.

IF: Inner focus lenses move the middle lens elements which does not change the lens' overall length when focusing. This results in better stability, which is useful for telephoto shooting.

DF: A dual focus lens. The focus ring on the lens pushes forward and backwards dis-engaging it so it does not rotate during autofocus.

Conv: These lenses are compatible with Sigma's teleconverters without and retain proper automatic exposure function.

Tamron Specific Lens Types and Abbreviations

AD : Anomalous Dispersion. Special optical glass design that reduces chromatic aberration by reducing the amount of "undesirable" light wavelength passage through the lens. See Tamron Learning Center :: Optical Technology for scientific explanation.

ASL : Aspherical Glass used in the lens.

Di : Digitally Integrated Design. This is the same as sigma's DG lenses and simply has extra coatings on the glass.

Di II : Lenses for Digital SLR Cameras Only (cameras with a APS-C size sensor) The same as Sigma's DC lenses.

IF : Internal focus.

LD : Low Dispersion Glass used in the lens.

SP : Super Performance. Tamron's "top shelf" high performance lenses sporting above average build quality, innovative design features and fine optical characteristics which set these lenses apart from standard lenses.

XR : Extra Refractive Index Glass.


EF 100-400 F/4.5-5.6L IS USM : An Electronic Focus lens with a telephoto zoom range from 100 to 400mm, with a maximum aperture of f/4.5 at the short (100mm) end and f/5.6 at the long (400mm) end. A member of Canon's Luxury lense lineup. Includes Image Stabilisation, and an Ultrasonic Motor for high speed silent focusing.

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