Canon EF lens mount
The EF lens mount allows all the Canon EF lenses to be used on any of the Canon EOS line of cameras made by Canon Inc. Unlike the EF's breech-lock predecessor, the FD mount, the EF mount uses a bayonet-style mount. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. All communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers.
History
When the EF mount was introduced in 1987, it had the largest mount diameter of 54 mm (internal) among all 35 mm SLR cameras, allowing large aperture lenses to be designed for the EOS system.
Unlike the standard autofocus lens mounting technology of the time, which used a motor in the camera body to drive the mechanics of the focus helicoid in the lens by using a transfer gear, the EF series used a motor inside the lens itself for focusing. This allowed for autofocusing lenses which did not require mechanical contacts in the mount mechanism, only electrical ones to supply power and drive information to the lens motor. Thus, the mounting mechanism was simpler and more durable. Also, the motors were designed for the particular lens they were installed in. One benefit of this arrangement is that if the motor in a lens breaks, other lenses will of course retain full function. If the motor of an in-body driven AF system fails, no autofocus is possible.
The EF series has since grown into a mature system with over 50 lenses for all types of applications, from landscapes to portraits to sports and photojournalism. Canon EF lenses also demonstrate successful commercialisation of mechanical and optical technologies, such as the Ultrasonic Motor (USM) drive, Image Stabilizer (IS), Diffractive Optics (DO) and using fluorite and aspherical elements in the construction of their L-series lenses for superb image quality.
Versatility
Although Canon does not endorse (and in fact warns against) the use of third-party lenses and adapters, the EF lens mount is ideal for the use of adapters, due to its large diameter and the relatively short flange focal distance of 44.0 mm[1]. It is thus possible to mount lenses using the Nikon F mount, Olympus OM, Leica R and universal M42 lens mounts (among others) by the use of a simple mechanical adapter. Ironically, the earlier FD mount is still not usable for general photography unless adapters with optical elements are used because its flange focal distance was only 42.0 mm; infinity focus would be lost with an adapter which lacks optical elements. The high quality Canon FD-EOS adapter is rare and quite expensive, as it was only sold to professionals with a substantial stock of FD telephoto lenses. It is only usable with certain FD telephoto lenses. Of course, with a purely manual connection, the aperture and focus controls of the lens cannot be controlled or read from the camera; the lens must be focused manually. In addition, since the only possible metering is through-the-lens, the lens must be manually stopped down to accurately meter at anything less than full aperture. (This is called stop-down metering.)
For other lens types, an adapter would act as an extension tube, causing the lens to lose the ability to focus to infinity. Alternatively, the lens adapters would include optical elements and act as weak teleconverters, as well as possibly losing considerable optical quality. Because of this, it is generally preferred to use lenses that can be mounted at their preferred offsets.
Third-party EF lenses
Third-party lenses compatible with EOS electronics are manufactured by Sigma, Tamron, and Tokina. The manufacturers of these lenses have reverse engineered the electronics of the EF lens mount. The use of these lenses is not supported by Canon. However, many users find these lenses to be cheaper, and sometimes superior alternatives to Canon lenses.
Related technologies
With the release of the EOS 300D Canon introduced a variation on the standard EF lens mount called EF-S.
Ultrasonic motor drive
Ultrasonic motor (USM) lenses first appeared with the introduction of the EF 300 mm f/2.8L USM lens in 1987. Canon is the first camera maker to successfully commercialise the USM technology. EF lenses equipped with USM drives have fast, silent and precise autofocus operations, and consume less power compared to other AF drive motors.
There are two types of USMs, the ring-type USM and the micromotor USM. Ring-type USM is always preferred because of its superior performance and efficiency, and it allows for full-time manual focus operations without switching out of AF mode. Micromotor USM is used in cheaper lenses to bring down the overall cost of the lens. It is possible to implement full-time manual focus even with micromotor USM; however, this is a somewhat inelegant solution, as it requires additional mechanical components, and so has not been widely implemented.
Some USM lenses are identified with a gold ring and the label "Ultrasonic" printed in gold on the lens barrel. All L lenses which have USM do not have the gold ring, but the red ring which denotes them as an L lens. However, they have the label "Ultrasonic" printed in red on the lens barrel.
Image stabilizer
A photograph can easily be ruined when handshake or vibration is introduced during long exposure shots. The Image Stabilizer (IS) counters such problems by optically correcting such shakes with accelerometers and lens groups that move in relation to the shakes, thus minimising or even eliminating minute vibrations from the image.
A general rule-of-thumb to overcome such vibrations would be to set the shutter speed equal to or faster than the reciprocal of the lens' focal length (e.g. 1/60s for a 50 mm lens). IS lenses can improve on this rule by up to three stops. That is, the same 50 mm lens could be used at 1/8s.
Canon has released several versions of the IS system. The original, first used in 1995's 75-300mm f/4-5.6 IS USM, takes approximately one second to stabilize, provides approximately two stops of stability, is not suitable for use on a tripod (if it cannot detect any motion, it may introduce unwanted motion of its own), and should not be used while panning. The next advance was released with the 300mm f/4L IS USM in 1997 and adds IS mode 2, which is for panning. Mode 2 detects whether panning is taking place horizontally or vertically, and only compensates for vibration in the plane perpendicular to the plane of panning. In 1999, with the release of the IS super-telephoto lenses (300mm f/2.8L IS USM through 600mm f/4L IS USM), tripod detection was added, so that the lens could be used on a tripod with IS enabled. In 2001, a new version of the Image Stabilizer was created for the 70-200mm f/2.8L IS USM. Startup time was reduced to approximately 0.5s and the amount of stabilization to three stops. The most recent improvement is used in the 70-200 f/4L IS USM, which allows up to four stops of stabilization.
Diffractive optics
Diffractive optics (DO) are used in lens designs that would otherwise require large and heavy chunks of glass. DO lenses, compared to non-DO lenses of similar focal length and aperture values, are usually smaller and lighter. In addition, DO lenses have superior chromatic aberration suppression characteristics that allow for sharper photographs; the chromatic aberration produced by DO lenses is opposite in direction to that produced by refractive lenses, and so the coupling of a diffractive element and a refractive element can effectively cancel chromatic aberration.
Nevertheless, DO elements are extremely expensive to make due to their high rejection rate, and therefore are introduced in limited EF lenses. Currently only the EF 400 mm f/4 DO IS USM and the EF 70-300 mm f/4.5-5.6 DO IS USM contain DO elements.
DO lenses are identified with a green ring on the lens barrel.
L-series lenses
Top-of-the-line Canon EF lenses are designated as L-series, or "Luxury" lenses.[1] L-series lenses have superior optical performance and are typically built with a solid construction to withstand constant use and harsh conditions. They can be recognized by a red ring around the front part of the lens. Most recent L lenses have sealing to help resist dust and water. L-series lenses are more frequently used by professionals and serious amateurs due to their high price and large mass.
An EF lens is designated as an L-series lens only when it contains at least one fluorite or ultra-low dispersion glass element, combined with super-low dispersion glass and ground aspherical elements. There are also some lenses which include one or more of these technologies yet which are not designated as L lenses. L-series lenses are also usually equipped with USM (particularly in recent years), IS, or both, but what sets an L-lens apart from the rest is its optical performance and its build quality. There are also several EF-S lenses which have similar or even better optical performance than Canon L-lenses, however due to the large number of professionals who use full-frame format Canon cameras (and the lack of 'L' quality build on the EF-S range), it is unlikely EF-S lenses will be labeled professional L-series lenses in the near future.
Larger sized L-series lenses, such as the 70-200mm and 100-400mm zooms and longer focal length primes (300mm+), usually have an off-white barrel (sometimes referred to as the color "putty") to reduce heat absorption under the sun that may otherwise affect the performance of the lens, as well as to identify Canon's lenses, for example at sporting events. However, shorter focal length L-series lenses can be black (such as the Canon EF 24-70mm f/2.8L and all L-lens primes under 300mm, with the single exception being the 200mm f/1.8 - which has been discontinued.). Therefore L-series lenses can be identified by either a lens barrel's off-white colour or, as on all L-lenses, the distinctive red ring on the lens barrel.
Owning a number of L-series lenses along with at least one professional EOS camera body is a requirement for admittance into the Canon Professional Service in most markets (for example, three for Europe and Australia, one for Hong Kong and Singapore).
List of EF lenses
The following is a list of EF lenses made by Canon. Please note that the "I", "II", "III", etc. after the focal length(s) indicates the latest generation number for that model.
The EF lenses are grouped below by their focal lengths:
- Zoom: for zoom lenses that have a range of focal lengths
- Prime: for prime lenses that have a single focal length
Zoom
| Focal length | Aperture | USM | IS | L-series | DO |
|---|---|---|---|---|---|
| 16-35 mm II | f/2.8 |  Yes
|
 No
|
Yes
|
No
|
| 17-35 mm | f/2.8 | No
|
No
|
Yes
|
No
|
| 17-40 mm | f/4 | Yes
|
No
|
Yes
|
No
|
| 20-35 mm | f/2.8 | No
|
No
|
Yes
|
No
|
| 20-35 mm | f/3.5-4.5 | Yes
|
No
|
No
|
No
|
| 22-55 mm | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 24-70 mm | f/2.8 | Yes
|
No
|
Yes
|
No
|
| 24-85 mm | f/3.5-4.5 | Yes
|
No
|
No
|
No
|
| 24-105 mm | f/4 | Yes
|
Yes
|
Yes
|
No
|
| 28-70 mm | f/2.8 | Yes
|
No
|
Yes
|
No
|
| 28-70 mm II | f/3.5-4.5 | No
|
No
|
No
|
No
|
| 28-80 mm | f/2.8-4 | Yes
|
No
|
Yes
|
No
|
| 28-80 mm II | f/3.5-5.6 | No
|
No
|
No
|
No
|
| 28-80 mm II | f/3.5-5.6 | Yes
|
No
|
No
|
No
|
| 28-80 mm V | f/3.5-5.6 | Yes
|
No
|
No
|
No
|
| 28-90 mm II | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 28-90 mm III | f/4-5.6 | No
|
No
|
No
|
No
|
| 28-105 mm II | f/3.5-4.5 | Yes
|
No
|
No
|
No
|
| 28-105 mm | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 28-135 mm | f/3.5-5.6 | Yes
|
Yes
|
No
|
No
|
| 28-200 mm | f/3.5-5.6 | Yes
|
No
|
No
|
No
|
| 28-200 mm | f/3.5-5.6 | No
|
No
|
No
|
No
|
| 28-300 mm | f/3.5-5.6 | Yes
|
Yes
|
Yes
|
No
|
| 35-70 mm | f/3.5-4.5 | No
|
No
|
No
|
No
|
| 35-70 mm | f/3.5-4.5A | No
|
No
|
No
|
No
|
| 35-80 mm III | f/4-5.6 | No
|
No
|
No
|
No
|
| 35-80 mm | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 35-105 mm | f/3.5-4.5 | No
|
No
|
No
|
No
|
| 35-105 mm | f/4.5-5.6 | No
|
No
|
No
|
No
|
| 35-135 mm | f/3.5-4.5 | No
|
No
|
No
|
No
|
| 35-135 mm | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 35-350 mm | f/3.5-5.6 | Yes
|
No
|
Yes
|
No
|
| 38-76 mm | f/4.5-5.6 | No
|
No
|
No
|
No
|
| 50-200 mm | f/3.5-4.5 | No
|
No
|
No
|
No
|
| 50-200 mm | f/3.5-4.5 | No
|
No
|
Yes
|
No
|
| 55-200 mm II | f/4.5-5.6 | Yes
|
No
|
No
|
No
|
| 70-200 mm | f/2.8 | Yes
|
Yes
|
Yes
|
No
|
| 70-200 mm | f/2.8 | Yes
|
No
|
Yes
|
No
|
| 70-200 mm | f/4 | Yes
|
Yes
|
Yes
|
No
|
| 70-200 mm | f/4 | Yes
|
No
|
Yes
|
No
|
| 70-210 mm | f/3.5-4.5 | Yes
|
No
|
No
|
No
|
| 70-210 mm | f/4 | No
|
No
|
No
|
No
|
| 70-300 mm | f/4.5-5.6 | Yes
|
Yes
|
No
|
Yes
|
| 70-300 mm | f/4-5.6 | Yes
|
Yes
|
No
|
No
|
| 75-300 mm | f/4-5.6 | Yes
|
Yes
|
No
|
No
|
| 75-300 mm III | f/4-5.6 | Yes
|
No
|
No
|
No
|
| 75-300 mm III | f/4-5.6 | No
|
No
|
No
|
No
|
| 80-200 mm | f/2.8 | No
|
No
|
Yes
|
No
|
| 80-200 mm | f/4.5-5.6 | Yes
|
No
|
No
|
No
|
| 80-200 mm II | f/4.5-5.6 | No
|
No
|
No
|
No
|
| 90-300 mm | f/4.5-5.6 | No
|
No
|
No
|
No
|
| 90-300 mm | f/4.5-5.6 | Yes
|
No
|
No
|
No
|
| 100-200 mm | f/4.5A | No
|
No
|
No
|
No
|
| 100-300 mm | f/4.5-5.6 | Yes
|
No
|
No
|
No
|
| 100-300 mm | f/5.6 | No
|
No
|
No
|
No
|
| 100-300 mm | f/5.6 | No
|
No
|
Yes
|
No
|
| 100-400 mm | f/4.5-5.6 | Yes
|
Yes
|
Yes
|
No
|
Prime
| Focal length | Aperture | Macro | Ultrasonic motor | Image stabilization | L-series | Diffractive optics | |
|---|---|---|---|---|---|---|---|
| Article | 14 mm | 2.8 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 15 mm (fisheye) | 2.8 | No
|
No
|
No
|
No
|
No
|
| Article | 20 mm | 2.8 | No
|
Yes
|
No
|
No
|
No
|
| Article | 24 mm | 1.4 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 24 mm | 2.8 | No
|
No
|
No
|
No
|
No
|
| Article | 28 mm | 1.8 | No
|
Yes
|
No
|
No
|
No
|
| Article | 28 mm | 2.8 | No
|
No
|
No
|
No
|
No
|
| Article | 35 mm | 1.4 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 35 mm | 2 | No
|
No
|
No
|
No
|
No
|
| Article | 50 mm | 1.0 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 50 mm | 1.2 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 50 mm | 1.4 | No
|
Yes
|
No
|
No
|
No
|
| Article | 50 mm II | 1.8 | No
|
No
|
No
|
No
|
No
|
| Article | 50 mm | 2.5 | Yes (Compact 1:2)
|
No
|
No
|
No
|
No
|
| Article | 85 mm | 1.2 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 85 mm II | 1.2 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 85 mm | 1.8 | No
|
Yes
|
No
|
No
|
No
|
| Article | 100 mm | 2 | No
|
Yes
|
No
|
No
|
No
|
| Article | 100 mm | 2.8 | Yes
|
No
|
No
|
No
|
No
|
| Article | 100 mm | 2.8 | Yes
|
Yes
|
No
|
No
|
No
|
| Article | 135 mm | 2 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 135 mm (SoftFocus) | 2.8 | No
|
No
|
No
|
No
|
No
|
| Article | 180 mm | 3.5 | Yes
|
Yes
|
No
|
Yes
|
No
|
| Article | 200 mm | 1.8 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 200 mm II | 2.8 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 300 mm | 2.8 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 300 mm | 2.8 | No
|
Yes
|
Yes
|
Yes
|
No
|
| Article | 300 mm | 4 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 300 mm | 4 | No
|
Yes
|
Yes
|
Yes
|
No
|
| Article | 400 mm II | 2.8 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 400 mm | 2.8 | No
|
Yes
|
Yes
|
Yes
|
No
|
| Article | 400 mm | 4 | No
|
Yes
|
Yes
|
No
|
Yes
|
| Article | 400 mm | 5.6 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 500 mm | 4 | No
|
Yes
|
Yes
|
Yes
|
No
|
| Article | 500 mm | 4.5 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 600 mm | 4 | No
|
Yes
|
No
|
Yes
|
No
|
| Article | 600 mm | 4 | No
|
Yes
|
Yes
|
Yes
|
No
|
| Article | 1200 mm | 5.6 | No
|
Yes
|
No
|
Yes
|
No
|
Exceptions
Canon has two types of lenses, Tilt-shift and Dedicated Macro lenses which are not designated EF, but are designated TS-E and MP-E respectively. TS stands for Tilt-shift while MP stands for Macro photo. These types of lenses, while not designated EF, are still compatible with the EF mount. These lenses are not designated as EF as these are manual-focus only lenses, and therefore are not Electro-Focus lenses. They do, however, retain electronic aperture control.
See also
Notes
- ^ W.J. Markerink maintains an excellent article on Camera Mounts & Registers which gives much more detail about flange focal distances and lens compatibility.
References
- Markerink, Willem-Jan. Camera Mounts & Registers. Retrieved on November 6, 2005.