Camera Lens Mount Guide

Making the right lens mount choice for your camera is essential to getting the optimum performance and compatibility for your needs as a photographer.

A lens mount on an interchangeable lens camera is an opening of a certain size that takes lenses made specifically for that mount and allows them to be attached. In the early days of photography, lenses and cameras were merely mechanically attached to one another without any communication between the two. With the advent of automatic metering and autofocus systems, lenses and cameras needed to establish electrical contacts in order to communicate with one another. Consequently, a lens attachment evolved into much more than merely a hole in the wall—rather, it became an interface between lenses and cameras.

The Canon RF mount is designed for full-frame sensors. It features a short flange distance of 20mm, which allows for more compact and lighter lens designs. The RF mount also supports faster data communication between the lens and the camera, enabling improved autofocus performance and advanced features like lens aberration correction.

The Canon RF-S mount is a variation of the RF mount tailored for Canon’s APS-C mirrorless cameras. While it maintains compatibility with RF lenses, it is optimized for smaller sensor sizes, making it ideal for photographers looking for a more compact system without sacrificing performance.

The standard mount for full-frame DSLR cameras made by Canon is the EF mount. A large variety of lenses, including the Tilt-Shift (TS-E) and Macro Photo (MP-E) series, are supported by its adaptability. These lenses are intended for specialist types of photography, such macro and architectural.

The EF-S mount is tailored for Canon’s APS-C DSLRs. These lenses are designed to be smaller, lighter, and more affordable than EF lenses, making them ideal for amateur photographers and enthusiasts. Despite their compact design, Canon EF-S lenses offer excellent image quality and cover a broad range of focal lengths, from wide-angle to telephoto.

Mirrorless cameras of the Canon EOS M series use the EF-M mount. Because of their lightweight and small construction, Canon EF-M lenses are ideal for everyday photography and travel. Although EF or EF-S mounts are not directly compatible with EF-M lenses, Canon provides adapters to close this compatibility gap, increasing lens choice and versatility.

There are a few critical measurements that must be taken when determining mount size, particularly when comparing one lens mount to another (you want to compare apples to apples). There are three measurements: throat size, inner diameter, and outer diameter.

Throat Size

Inner Diameter

Outer Diameter

Flange distance is the distance between the film/sensor plane and the mounting flange, which is the outside section of the lens mount as viewed from the side. It is sometimes referred to as "flange focal distance," "flange back distance," or just "register." Flange lengths frequently range significantly across various camera systems, much as throat size, inner diameter, and outer diameter of different mounts.

Lens mount identifiers, such as EF, RF, and EF-S, help users quickly recognize lens compatibility with their camera bodies. These identifiers are often included in the lens's name or specifications, simplifying the process of selecting compatible lenses.

The sensor size (full-frame, APS-C) and its resolution significantly impact lens performance and suitability. Full-frame sensors generally require lenses with larger image circles to cover the entire sensor area, while APS-C sensors can use smaller, lighter lenses. High-resolution sensors demand high-quality lenses to resolve fine details and avoid image degradation.

Selecting a lens mount requires careful consideration of compatibility. Make sure the lens mount you choose works with both the body of your camera and any other lenses you may have.

Related: View Canon Lens Mount Compatibility Chart

Using Canon Lenses with Other Cameras

Using Other Brand Lenses with Canon Cameras

Other Lens Mounts

A crucial choice that impacts both the functionality of your camera and your overall photographic experience is selecting the appropriate lens mount. You may choose the Canon lens mount that best meets your needs by being aware of the many kinds of lens mounts available, the things to look for when choosing a lens mount, and the adaptability of lens mount adapters.