The EF mount reverses this logic, providing the bayonet on each lens, and a receptacle on the camera body.

[2] The EF series includes over eighty lenses, encompassing focal lengths from 8 to 1200 mm.

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.

Compatible third-party lenses with the EF lens mount are manufactured by Yongnuo, Samyang, Schneider, Sigma, Tamron, Tokina, Cosina and Carl Zeiss.

Sometimes compatibility problems arise, as no third party has access to Canon's specifications for camera-to-body communication.

Red Digital Cinema Company offers various camera models that can be equipped with an electronic EF-mount.

For Sony E-mount various adaptors enable using EF-mount lenses with full electronic control.

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.

This feature, while not a control or switch, is useful to the photographer for determining, or setting, the lens's focus distance.

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.

Ring-type USM allows for full-time manual focus (FT-M) operations without switching out of AF mode.

It is possible to implement FT-M even with micromotor USM; however, it requires additional mechanical components, and the vast majority of micro-USM lenses do not offer such capability.

Nano USM was introduced in 2016 with the release of Canon's latest iteration of the EF-S 18–135mm lens.

It is intended to offer the AF speed of ring-type USM with the quietness of STM mechanisms (see below).

L lenses with USM don't have the gold ring, but they still have the word "Ultrasonic" printed on the lens barrel.

Canon announced stepping motor (STM) lenses first in June 2012, alongside the EOS 650D/Rebel T4i/Kiss X6i.

[12] Unlike USM, STM lenses use focus-by-wire to enable full-time manual mode.

Two main disadvantages are linked to focus-by-wire: First, the need to computationally process the input before the intended action is executed leads to a sometimes perceptible lag.

All stepping-motor lenses are marked with the letters "STM" on the front of the lens as part of the model designation.

Canon has released several versions of the IS system, including the following: All EF lenses that support IS have the words "Image Stabilizer" written on the lens.

On some of Canon's larger telephoto lenses, the words "Image Stabilizer" are etched onto a metal plate affixed to the lens.

[17] L series lenses are compatible with the full range of EF or EF-S mounts and, as they are aimed at the high-end user, most also include environmental or weather sealing and a constant maximum aperture.

Distinctive visual cues include a red ring around the lens and an off-white colour on longer-focal-length models.

The latter also helps to reflect light and reduce heat absorption and subsequent internal expansion of lens components that can affect the image quality of long focal length lenses.

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 "I", "II", "III" Roman numeral suffix after the focal length(s) indicates the generation number.

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.

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