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Canon lens terminology explained: How to read a lens name

You can tell a lot about a lens just by looking at its full name. Understanding what it means will be very helpful when you are trying to decide which lens to buy for your photography needs. Each lens name is made up of a series of letters and numbers that provide useful information about its characteristics and compatibilities. There are four main elements that make up every lens name: lens mount, focal length, aperture and any specific technologies used in the lens. At Canon we use specific terminology to reference our lenses and understanding this will help you choose the right lens for you. So, whether you’re a complete beginner, or want to refresh your knowledge on Canon lens specifications, use our guide to help you on your photography journey.

Lens Mount Type

At Canon we have four different types of lens mount: RF, RF-S, EF, EF-S and EF-M. Put simply, a lens mount is the interface between a camera body and a lens. This feature allows for interchangeable lenses. Depending on your camera, different lens types can be used with or without a lens mount adapter.

RF & RF-S

e.g. Canon RF 24-105mm F4L IS USM Lens

RF and RF-S lenses are specifically designed for EOS R system mirrorless cameras.

Good to know: Cameras from the EOS R range can be used with EF and EF-S lenses, when used with an adapter.

EF

e.g. Canon EF 85mm f/1.8 USM Lens

EF stands for Electronic Focus and is Canon’s longest established lens mount. It also has the widest compatibility and works with a wide range of Canon cameras. These lenses fit the entire EOS DSLR (Digital SLR) range including:

  • Full-frame sensor DSLRs
  • APS-C (Crop sensor DSLRs)

    Good to know: EF lenses can also be used with an EOS M (EF-M mirrorless mount) and EOS R (full-frame mirrorless mount) cameras when used with an adapter.

EF-S

e.g. Canon EF-S 60mm f/2.8 Macro USM Lens

EF-S lenses are designed for APS-C (also known as crop sensors) DSLRs and are not compatible with full-frame DSLR cameras. By designing for the smaller APS-C sensor, the lens can be made smaller and lighter. For more information on whether your camera is an APS-C or full-frame DSLR, check the specifications on the individual product description. Good to know: EF-S lenses can also be used with EOS M (EF-M mirrorless mount) and R (full-frame mount) cameras, when used with an adapter.

EF-M

e.g. Canon EF-M 32mm f/1.4 STM Lens

EF-M lenses are designed specifically for EOS M (mirrorless) cameras.
Good to know: When used with an adapter, EOS M cameras can use EF and EF-S lenses.

Specialist Lenses

We also have other specialist lenses including the TS-E (Tilt & Shift) and MP-E which have an EF mount. A TS-E lens allows the user to physically adjust the front of the lens, move it up and down, in order to adjust the apparent angle and plane of focus. This type of lens is mainly for specialist users and is ideal for a range of photography such as architecture, product and landscape photography.

Focal Length

mm – Focal Length (e.g. Canon EF 135mm f/2L USM Lens)

The focal length measures the range of a lens showing its shortest and longest distance. The bigger the number (the ‘longer’ the focal length), the narrower the angle of view. This means subjects will appear to be closer to the camera.

View of St. Paul's Cathedral at 28mm, showing a wide field of view with more of the scene visible.
28mm 		View of St. Paul's Cathedral at 85mm, showing a standard perspective with less of the scene visible.
85mm 		View of St. Paul's Cathedral at 135mm, showing a narrower field of view of a telephoto lens.
135mm 		View of St. Paul’s Cathedral at 200mm, showing a tight telephoto view with strong background compression.
200mm 		View of St. Paul’s Cathedral at 300mm, showing a very narrow telephoto field of view with distant details.
300mm 		View of St. Paul’s Cathedral at 600mm, showing a very tight telephoto crop with minimal context.
600mm

Aperture

f/ or F – Aperture (e.g. Canon RF 15-35mm F2.8L IS USM Lens)

Expressed as f-numbers or f-stop, aperture is the part of the lens where you control the amount of light that goes to the camera sensor. The smaller the number, the bigger the aperture and the more light can get to the camera. Controlling the aperture can benefit you in different ways. A wider aperture will create a very blurred background but a sharp subject or foreground. For example, F2.8 lets in more light than F11. Apertures of F2.8 and below are better suited for night photography and portraits.

Portrait at f/1.8 demonstrating very shallow depth of field and strong background blur.
F/1.8 		Portrait at f/4 showing moderate background blur.
F/4 		Portrait at f/8 showing deeper depth of field with more detail in the background.
F/8 		Portrait at f/16 demonstrating deep depth of field where most of the scene appears sharp.
F/16

Constant Maximum Aperture

If a zoom lens only has a single f-stop in its name (e.g. F2.8) instead of a range (e.g. F3.5-6.3), this means that it’s got a constant maximum aperture. On zoom lenses without this feature, the aperture gets smaller as you zoom in, letting in less light. For example, the RF-S 18-150mm F3.5-6.3 IS STM Lens would have f/3.5 at 18mm, but this drops to f/6.3 at 150mm. Higher end lenses with a constant maximum aperture, like the RF 15-35mm F2.8L IS USM Lens keep their maximum aperture throughout the zoom range. This makes the lens easier to work with, because you won’t need to adjust settings to compensate for a changing aperture as you zoom. 

Generation

Written in Roman numerals, this tells you where the lens sits in terms of development. When a lens design is improved, it gets a new number. (eg. III is the newer version of II)

Technologies

Technologies offer more information in terms of features your lens has, and how it can help your photography.

Close-up of a red letter L printed on the side of a Canon lens.

L – Luxury Lens (e.g. Canon RF 70-200mm F2.8L IS USM Lens)

L stands for Luxury. L lenses are professional lenses with great optical quality. They are used by professional photographers and offer the ultimate quality and performance.

Good to know: L lenses usually have a red ring around the end.

Canon telephoto lens resting on a camera bag in a flowering field.

DO – Diffractive Optics (e.g. Canon EF 400mm f/4 DO IS II USM Lens)

DO stands for Diffractive Optics and shows that a lens uses special elements to help make them more compact without compromising on quality.

Good to know: These are usually differentiated by a green ring around the front of the lens.

Portrait of a woman in an intricate dress on a blurry background.

DS – Defocus Smoothing coating (e.g. Canon RF 85mm F1.2L USM DS Lens)

DS lenses make the bokeh (out of focus elements) in a picture a lot smoother compared to regular lenses, bringing more focus to the subject of the photo.

Image Stabilisation

IS – Image Stabilisation (e.g. Canon EF-M 55-200mm f/4.5-6.3 IS STM Lens)

Image Stabilisation is a system that reduces the effects of camera shake for a sharper image. You will know if your lens has image stabilisation because there will be an “IS” in the name.

Good to know: Image Stabilisation is measured in stops. The more stops a lens has, the more effective the IS will be.

Blurry image of a small waterfall demonstrating Image Stabilisation being turned off.
IS OFF		 Sharp image of a small waterfall demonstrating Image Stabilisation being turned on.
IS ON

Focusing Motor

STM

STM stands for Stepper Motor. This has quieter, smoother focusing, making it ideal for filming – but is still great for photos. STM is found in many different lenses.Macro lenses are designed for close-up photography and capture details and close-ups. The minimum focusing distance of this lens is smaller, meaning you can get a lot closer to your subject.

USM

USM stands for Ultrasonic Autofocus Motor. This motor can be found in lots of our lenses. These lenses are fast and have a manual override, making them ideal for stills. Take a closer look at how USM works

Nano USM

Though it has “USM” in the name, Nano USM has benefits of both USM and STM. It offers fast, smooth and quiet focusing, making it ideal for action photography and videography. Take a closer look at how Nano USM works.

VCM

VCM stands for Voice Coil Motor and it’s the latest development in Canon’s autofocus motor technology. It uses magnetic force to move elements quickly, precisely and quietly. This makes it especially well-suited for video recording. Macro lenses are designed for close-up photography and capture details and close-ups. The minimum focusing distance of this lens is smaller, meaning you can get a lot closer to your subject.

Macro

Macro

e.g. Canon EF-S 35mm f/2.8 Macro IS STM Lens

Macro lenses are designed for close-up photography and capture details and close-ups. The minimum focusing distance of this lens is smaller, meaning you can get a lot closer to your subject.