Canon EF lens mount

Number of Canon EF lenses sold over time (red), compared with Nikon F mount lenses (blue)

The EF mount replaces its predecessor, the FD mount. The standard autofocus lens mounting technology of the time used a motor in the camera body to drive the mechanics of the focus helicoid in the lens by using a transfer lever. The key innovation of the EF series was to use a motor inside the lens itself for focusing. This allowed for autofocusing lenses which did not require mechanical levers in the mount mechanism, only electrical contacts to supply power and instructions to the lens motor. The motors were designed for the particular lens they were installed in.

The EF mount reversed the mechanical logic of the FD mount. The FD mount provided the three-eared bayonet fitting on the camera body, and each FD lens provided a breech-lock receptacle to register and fasten the lens to the bayonet. The EF mount reverses this logic, providing the bayonet on each lens, and a receptacle on the camera body.

The EF mount also changed the logical clamping action of the bayonet receptacle to improve the tactical operation. Attaching an FD lens to a camera body required two hands: one to hold the lens in position, and a second to twist the breech-lock ring to rigidly lock the lens to the camera. The EF mount instead provides leaf springs in the receptacle, which hold the registration surfaces of the lens and receptacle together along the optical axis, while the manual twisting action engages a spring-loaded registration pin in the receptacle which drops into a recess provided on the bayonet fitting, locking the rotation. This EF mount feature provided the convenience of attaching EF lenses with one hand (holding the lens and twisting), versus two hands (one to hold the lens, one to twist the breech-lock) required for the FD attachment. An EF lens may also be removed with one hand by gripping the base of the lens and pressing the nearby release button with the tip of thumb. The one-handed skillful operation of the EF mount allows changing lenses in handheld photography, since the other hand is freed to hold the camera body.

When the EF mount was introduced in 1987, it had the largest mount diameter (54 mm internal) among all 35 mm SLR cameras.[2]

The EF series includes over eighty lenses, encompassing focal lengths from 8 to 1200 mm. Many EF lenses include such features as Canon's ultrasonic motor (USM) drive, an image stabilization system (IS), diffractive optics (DO) and, particularly for L-series lenses, fluorite and aspherical lens elements.

The EF mount of a Canon EOS 50

Electronics of an EF-S lens

Its large diameter and relatively short flange focal distance of 44.0 mm allows mechanical adaptation of EF camera bodies to many types of non-EF lenses.[3] It is 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 mechanical adapter without electronic control of the aperture or autofocus. In contrast, parfocal adaptation of EF lenses to non-EF camera bodies is not possible with only a mechanical adapter that does not contain optical elements.

EF mount lenses are somewhat compatible with newer Canon bodies, though the reverse is not true:

• EF-S lens mount cameras can mount EF lenses without an adapter
• EF-M lens mount cameras can mount EF lenses with an EF-EOS M adapter[4]
• RF mount cameras can mount EF lenses with a variety of adapters

Lenses for the earlier Canon FD lens mount are not usable for general photography on an EF mount cameras, unless adapters with optical elements are used because they are made for a flange focal distance of only 42.0 mm. Most of these lenses require autofocus and aperture motors inside the body which isn't available in EOS bodies. Infinity focus would be lost with an adapter which lacks optical elements. The Canon FD-EOS adapter is rare and is only usable with certain FD telephoto lenses. With a manual connection, the aperture and focus controls of the lens cannot be controlled or read from the camera; the lens must be focused manually. 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.)

An EF lens showing its different controls and features

Canon EF lenses typically have a number of controls, switches and physical features, used by the photographer to control the lens. The types and number of the controls can vary from lens to lens. With the most basic lenses having only a few, to the most complex having over a dozen different controls and switches.

This is a list of the different controls and switches found on most Canon EF lenses, along with a detailed description on what they are used for.

Lens mount index: This raised, round red mark is found on all EF lenses. It is used for matching the EF lens mount to the mount on an EOS body, so one can connect the lens to the body quickly.

Focusing ring: This control, found on most EF lenses, is used for focusing the lens. It is usually a ring on the lens body, that can be turned.

Zoom ring: This control is found on most EF zoom lenses. It is used for changing the focal length of the lens. The zoom ring usually has certain, common, focal lengths marked on it. To set the zoom ring to any given focal length, one must turn the ring so that the marked focal length matches the zoom index. The zoom index is typically a white, or black, line found next to the zoom ring.

Distance scale of an EF lens

Distance scale window: This feature is found on many EF lenses. This feature, while not a control or switch, is useful to the photographer for determining, or setting, the lens's focus distance. It is used in conjunction with the Focusing ring. When rotated, the distance scale will also rotate to show the changing focus distance. On some lenses the distance scale also has an infrared index. These are shown as red markings below the distance scale. This is used for making focus adjustments when the photographer is doing infrared photography, as lenses typically focus infrared light at a different point than visible light, and therefore achieving correct focus using visible light will result in an out-of-focus infrared image. To make an adjustment, first focus the subject, then turn the Focusing ring so it matches the corresponding infrared index mark.

Focus mode, and focusing range switches

Focus mode switch: This switch is found on most EF lenses that have an autofocus feature. It is used for setting the lens to either autofocus mode, or manual focus. When set to autofocus mode (AF), the lens will autofocus when directed to by the camera. When set to manual focus (MF), the lens is focused using the Focusing ring. Some lenses support full-time manual focusing (FT-M), which allows the photographer to focus the lens manually even with the mode switch set to AF, without damaging the lens (as could happen if a lens without FT-M is manually focused while in AF mode).

Focusing distance range limiter switch: This switch is found on most longer focal length lenses, and macro lenses. It is used for limiting the focusing distance range of the lens when using it in autofocus mode. Most lenses have two settings; these are usually full focus range (from minimum focus distance to infinity), and distant focus range (from halfway point of focus range to infinity). Other lenses have three settings, with the additional setting usually being near focus range (from minimum focus distance to halfway point of focus range). Longer focal length lenses and macro lenses have a relatively long travel distance for the focusing mechanism inside the lens; this feature shortens the autofocus time. When the photographer knows they will not need a certain part of the focus distance range, limiting it will help shorten the autofocus time, and possibly prevent "focus hunting".

Soft focus ring: This ring is found only on the 135 mm 'Soft Focus' prime lens, and enables a variable soft focus effect from completely sharp (0) to very soft (2), although it has little effect when used with apertures over f/5.6. Although the ring can be set to any position, two 'stops' are implemented at positions 1 and 2.

Both types of image stabilizer switches

Image stabilizer switch: This switch is found on all EF lenses that feature an image stabilizer. It is used for turning the image stabilizer "on"( | ), or "off"( o ).

Image stabilizer mode switch: This switch is found on many EF lenses that feature an image stabilizer, particularly those of longer focal lengths. The switch has two settings on most lenses: Mode 1 and Mode 2. The newest IS Mark II versions of certain EF super telephoto lenses (the 300mm f/2.8L,[6] 400mm f/2.8L,[7] 500mm f/4L,[8] and 600mm f/4L[9]), plus the 200–400mm f/4L IS[10] and 100–400mm f/4–5.6L IS II,[11] have a third setting, Mode 3. Mode 1 is normal mode, used for typical photography, where the subject does not move. Mode 2 is used for panning; this is useful for sports or wildlife photography, where the subject moves constantly and one will need to pan. Mode 3, intended to track action, is similar to Mode 2 in that it ignores panning; however, it only applies stabilization when the shutter is released—the viewfinder image is not stabilized.[9] One should not use Mode 1 for panning as this will typically cause blurred photographs; the image stabilizer will attempt to correct for all motion, including the panning motion, but cannot do so due to the limited range of motion of the IS mechanism. Older lenses that have an image stabilizer, but do not feature this switch, are permanently in Mode 1. Some newer lenses, such as the Canon EF-S 18-200mm lens, are able to detect if they are being panned in either axis and will automatically disable the stabilization for the axis parallel to movement and therefore do not require this switch.

Autofocus stop buttons: These buttons are found on some super telephoto EF lenses, evenly spaced around the front collar of the lens. They are used for temporarily stopping the autofocus feature of the lens. Only one button needs to be pressed to activate the feature. To use this button, one must first have the autofocus active, then when one wishes to halt autofocus, one presses and holds the button. To resume autofocus, one releases the button. Some newer bodies allow these buttons to be assigned to perform other functions; for instance, the Canon EOS 7D allows the photographer to set these buttons to perform any of six functions.

Focus preset: The focus preset feature is found on most super telephoto EF lenses. The focus preset feature uses one switch, one button, and one ring. It is used for presetting a given focus distance into memory, so that the photographer can quickly recall the focus distance, without the need for autofocus. The switch has three settings "off"( o ), "on"( | ), or "on with sound"( ((- ), and is used for turning on the feature, and deciding if sound is desired. The "set" button is used for saving the focus distance into memory. The focus preset ring is used for recalling the memory save point. It is a thin knurled ring, usually located in front of the Focusing ring. To use this feature, one must set the switch to either "on" or "on with sound", focus the lens to the desired distance, then press the "set" button. After this, when the feature is turned on, the photographer can turn the focus preset ring, and the lens will recall and focus quickly to the distance that was saved. This feature is useful for sports and birding photography (for instance, to allow rapid focusing on the goal or on a spot where the birds may perch).

Rear gel filter holder on an EF lens

Filter mounting: This mount is used for attaching filters to EF lenses. There are three types: front threaded mount, inner drop-in mount, and rear gelatin holders. Front threaded filters are used on most lenses, and are attached by threading and tightening the filter. Inner, drop-in filter mounts are used on super telephoto EF lenses. They are attached by first pressing the two buttons on the filter mount, and pulling it out. Then either a round threaded filter is attached, or one can use a gelatin filter. Rear gelatin filter holders are used by cutting out a sheet of gelatin, to the size shown on the back of the lens and then sliding it into the holder. Filter mounts are useful for all types of photography, and every EF lens has either one or two of the three types used.

Lens hood mount: This feature is found on most EF lenses. This mount is used for attaching the lens hood. The hood mount is of a bayonet style on most EF lenses, though a clip-on style hood mount is used for a small selection of current lenses.

Tripod collar: This feature is found on most longer focal length lenses, and macro lenses. The tripod collar is used for attaching the tripod ring. There are two main styles of tripod rings. One type is opened up, placed on the lens' tripod collar, then closed and tightened. The other type does not open, but instead is slid up the lens from the mount end (which can only be done when the lens is not mounted on a camera body) and tightened. To set the tripod ring so that it is level with the lens, rotate the ring until the index mark on the tripod ring matches the index mark on the distance scale. The tripod ring is used for attaching a tripod/monopod near to the point of balance of the lens-body combination, more conveniently than the camera body. In the case of larger and heavier lenses, there is also less strain on the lens mount if the body is supported by the tripod-mounted lens than if the lens were to be supported by a tripod-mounted body.

In 1987 Canon was the first to use USM (Ultra Sonic Motor) with the Canon EF 300mm f/2.8L USM.[19]

In 1989 Canon was the first to create a full frame f/1.0 AF (AutoFocus) lens and the only one until today with the Canon EF 50mm f/1.0L USM.

In 1993 Canon was the first to create an interchangeable 10× superzoom lens for SLR cameras. That lens was Canon EF 35-350mm f/3.5-5.6L USM.

In 1993 Canon created the first Super UD (Ultra low Dispersion) lens with the Canon EF 400mm f/5.6L USM.

In 1995 Canon created the first lens with IS (Image Stabilization). That lens was the Canon EF 75-300mm f/4-5.6 IS USM.

Canon in 2001 was the first to create a lens with DO (multi layered Diffractive Optical element) element. That lens was the Canon EF 400mm f/4 DO IS USM.

Canon in 2008 created the first lens with SWC technology (Subwavelength Structure Coating). That lens was the Canon EF 24mm f/1.4L II USM.

Canon in 2009 created the first lens with Hybrid IS (Image Stabilization) which compensates both angle camera shake and shift camera shake with the Canon EF 100mm f/2.8L Macro IS USM.

Canon in 2010 was the first to create a lens with Fluoride coating. That lens was the Canon EF 70-300mm f/4-5.6L IS USM.

Canon in 2011 made the first fisheye zoom lens, both circular and rectangular. That lens was the Canon EF 8-15mm f/4L Fisheye USM.

Canon in 2012 made the first wide angle lens with Image Stabilization. That lens was the Canon EF 24mm f/2.8 IS USM.

Canon in 2013 created the first telephoto with built-in 1.4× extender. That lens was Canon EF 200-400mm f/4L IS USM Extender 1.4x.[19]

The communication protocol between the camera and the lens is 8-data-bit, 1-stop-bit SPI (mode 3). The pins, from right to left on the lens, are:

Canon EF mount pins[2][20]

Name	Function	Notes
VBat	+6 V to power internal lens focus motors	Present on all EOS bodies and lenses
P-Gnd	Power ground
P-Gnd
VDD	+5.5 V Digital logic power
DCL	Data from camera to the lens (MOSI)
DLC	Data from the lens to the camera (MISO)
LCLK	Camera body generated clock signal (SCLK, CPOL=1)
D-GND	Digital logic ground
COM1	Teleconverter common[21][22][23]	Only on most L-series and some macro lenses
EXT0	Short to COM1 for 'Life Size Converter' and 1.4× teleconverter
EXT1	Short to COM1 for 2× and 1.4× teleconverter

The information from the lens is used by the camera body for focusing and metering, and with digital camera bodies it is used to record the lens parameters in the Exif data in the images.

All L series primes 135mm or longer, the 400mm DO, the 70–200mm zooms, the 100–400mm zooms, the 200–400mm zoom and the 50mm Compact Macro have three additional communication pins. These additional pins are used by the Canon Extender EF adapters and the Life-Size Converter EF to indicate to the lens the change in focal length so that it is able to report the correct focal length and aperture to the camera body when mounted on a teleconverter. The lens also reduces autofocus speed when a teleconverter is attached to improve autofocus accuracy.

The "I", "II", "III" Roman numeral suffix after the focal length(s) indicates the generation number. While I is used in the table below, it is not used in official Canon model numbers; the original model lacks a Roman numeral and only the second and subsequent generations have them. Roman numerals are used only when the entire model designation—focal length(s), aperture, IS, DO, L status, and motor mechanism—is identical from one version to the next. This means, for example, that when Canon introduced IS to lenses whose prior versions lacked that feature (24mm, 28mm, 35mm IS primes in 2012, 16–35mm IS zoom in 2014), the first IS versions lacked Roman numerals.

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

Canon EF 35–70 mm f/3.5–4.5 lens

Focal length	Aperture	Introduction	USM	IS	L-series	DO	Filter size
8–15 mm (fisheye)	f/4	2010	Yes	No	Yes	No	rear
11–24 mm	f/4	2015	Yes	No	Yes	No	rear
16–35 mm I	f/2.8	2001	Yes	No	Yes	No	77 mm
16–35 mm II	f/2.8	2007	Yes	No	Yes	No	82 mm
16–35 mm III	f/2.8	2016	Yes	No	Yes	No	82 mm
16–35 mm IS	f/4	2014	Yes	Yes	Yes	No	77 mm
17–35 mm	f/2.8	1996	Yes	No	Yes	No	77 mm
17–40 mm	f/4	2003	Yes	No	Yes	No	77 mm
20–35 mm	f/2.8	1989	No	No	Yes	No	72 mm
20–35 mm	f/3.5–4.5	1993	Yes	No	No	No	77 mm
22–55 mm	f/4-5.6	1998	Yes	No	No	No	58 mm
24–70 mm	f/2.8	2002	Yes	No	Yes	No	77 mm
24–70 mm II	f/2.8	2012	Yes	No	Yes	No	82 mm
24–70 mm	f/4	2012	Yes	Yes	Yes	No	77 mm
24–85 mm	f/3.5-4.5	1996	Yes	No	No	No	67 mm
24–105 mm	f/4	2005	Yes	Yes	Yes	No	77 mm
24–105 mm II	f/4	2016	Yes	Yes	Yes	No	77 mm
24–105 mm STM	f/3.5-5.6	2014	No	Yes	No	No	77 mm
28–70 mm	f/2.8	1993	Yes	No	Yes	No	77 mm
28–70 mm II	f/3.5-4.5	1988	No	No	No	No	52 mm
28–80 mm	f/2.8-4	1989	Yes	No	Yes	No	72 mm
28–80 mm	f/3.5-5.6	1996	No	No	No	No	58 mm
28–80 mm II	f/3.5-5.6	1999	No	No	No	No	58 mm
28–80 mm I	f/3.5-5.6	1991	Yes	No	No	No	58 mm
28–80 mm II	f/3.5-5.6	1993	Yes	No	No	No	58 mm
28–80 mm III	f/3.5-5.6	1995	Yes	No	No	No	58mm
28–80 mm IV	f/3.5-5.6	1996	Yes	No	No	No	58 mm
28–80 mm V	f/3.5-5.6	1999	Yes	No	No	No	58 mm
28–90 mm	f/4-5.6	2000	Yes	No	No	No	58 mm
28–90 mm II	f/4-5.6	2003	Yes	No	No	No	58 mm
28–90 mm III	f/4-5.6	2004	No	No	No	No	58 mm
28–105 mm	f/3.5-4.5	1992	Yes	No	No	No	58 mm
28–105 mm II	f/3.5-4.5	2000	Yes	No	No	No	58 mm
28–105 mm	f/4-5.6	2002	Yes	No	No	No	58 mm
28–135 mm	f/3.5-5.6	1998	Yes	Yes	No	No	72 mm
28–200 mm	f/3.5-5.6	2000	Yes	No	No	No	72 mm
28–200 mm	f/3.5-5.6	2000	No	No	No	No	72 mm
28–300 mm	f/3.5-5.6	2004	Yes	Yes	Yes	No	77 mm
35–70 mm	f/3.5-4.5	1987	No	No	No	No	52 mm
35–70 mm	f/3.5-4.5A	1988	No	No	No	No	52 mm
35–80 mm III	f/4-5.6	1995	No	No	No	No	52 mm
35–80 mm	f/4-5.6	1992	Yes	No	No	No	52 mm
35–80 mm Power Zoom	f/4-5.6	1990	Yes	No	No	No	52 mm
35–105 mm	f/3.5-4.5	1987	No	No	No	No	58 mm
35–105 mm	f/4.5-5.6	1992	Yes	No	No	No	58 mm
35–135 mm	f/3.5-4.5	1988	No	No	No	No	58 mm
35–135 mm	f/4-5.6	1990	Yes	No	No	No	58 mm
35–350 mm	f/3.5-5.6	1993	Yes	No	Yes	No	72 mm
38–76 mm	f/4.5-5.6	1995	No	No	No	No	52 mm
50–200 mm	f/3.5-4.5	1987	No	No	No	No	58 mm
50–200 mm	f/3.5-4.5	1988	No	No	Yes	No	58 mm
55–200 mm	f/4.5-5.6	1998	Yes	No	No	No	52 mm
55–200 mm II	f/4.5-5.6	2003	Yes	No	No	No	52 mm
70–200 mm	f/2.8	2001	Yes	Yes	Yes	No	77 mm
70–200 mm II	f/2.8	2010	Yes	Yes	Yes	No	77 mm
70–200 mm III[24]	f/2.8	2018	Yes	Yes	Yes	No	77 mm
70–200 mm	f/2.8	1995	Yes	No	Yes	No	77 mm
70–200 mm	f/4	2006	Yes	Yes	Yes	No	67 mm
70–200 mm II[24]	f/4	2018	Yes	Yes	Yes	No	72 mm
70–200 mm	f/4	1999	Yes	No	Yes	No	67 mm
70–210 mm	f/3.5-4.5	1990	Yes	No	No	No	58 mm
70–210 mm	f/4	1987	No	No	No	No	58 mm
70–300 mm	f/4.5-5.6	2004	Yes	Yes	No	Yes	58 mm
70–300 mm	f/4-5.6	2005	Yes	Yes	No	No	58 mm
70–300 mm	f/4-5.6	2010	Yes	Yes	Yes	No	67 mm[25]
70–300  mm II	f/4-5.6	2016	Yes	Yes	No	No	67 mm[26]
75–300 mm	f/4-5.6	1991	Yes	Yes	No	No	58 mm
75–300 mm II	f/4-5.6	1995	No	No	No	No	58 mm
75–300 mm III	f/4-5.6	1999	Yes	No	No	No	58 mm
80–200 mm	f/2.8	1989	No	No	Yes	No	72 mm
80–200 mm	f/4.5-5.6	1992	Yes	No	No	No	52 mm
80–200 mm II	f/4.5-5.6	1990	No	No	No	No	52 mm
90–300 mm	f/4.5-5.6	2003	No	No	No	No	58 mm
90–300 mm	f/4.5-5.6	2002	Yes	No	No	No	58 mm
100–200 mm	f/4.5A	1988	No	No	No	No	58 mm
100–300 mm	f/4.5-5.6	1990	Yes	No	No	No	58 mm
100–300 mm	f/5.6	1987	No	No	No	No	58 mm
100–300 mm	f/5.6	1987	No	No	Yes	No	58 mm
100–400 mm	f/4.5-5.6	1998	Yes	Yes	Yes	No	77 mm
100–400 mm II	f/4.5-5.6	2014	Yes	Yes	Yes	No	77 mm
200–400 mm	f/4	2013	Yes	Yes	Yes	No	52 mm rear

Two EF lenses and an EF-S lens (center).

Canon has two further types of lenses compatible with the EF mount: Tilt-shift and the 1-5x Macro lens, which are not designated EF, but TS-E and MP-E respectively. TS stands for Tilt-shift while MP stands for macro-photo. These types of lenses are not designated EF as they are manual-focus only lenses. They do, however, retain electronic aperture control as well as focus confirmation.

• Canon FD lens mount
• Canon EF-S lens mount
• Canon EF-M lens mount
• Canon RF lens mount

• Markerink, Willem-Jan. Camera Mounts & Registers. Retrieved on 6 November 2005.
• tiffen.com. Lens To Filter Chart. For list of filter sizes.

• EF Lenses at the Canon Camera Museum
• List of all Canon SLR lenses with technical specifications