What Is a STM Lens? 

What Is a STM Lens featured photo

Nothing is more confusing and overwhelming than buying a camera lens. You have probably come across various focal lengths and the zoom vs. prime debate. But you might have also encountered unfamiliar acronyms like STM and USM.

STM refers to a lens that uses a stepping motor for focus. This autofocusing system moves in fixed steps to ensure smooth and silent performance.  

However, STM lenses offer other benefits, which we will explore later. This article also covers the applications of these lenses to help you decide if they suit your needs. You will even learn how STM differs from USM lenses below.

What Is a STM Lens?

Canon STM lens

STM stands for stepping motor. The acronym refers to a Canon lens autofocus system. However, most camera brands also include a stepping motor on their lenses but call them by other names. 

STM lenses use a stepping motor to move the focusing ring. This component rotates in fixed steps to prevent sudden movement. It delivers a smooth and nearly silent autofocusing performance.

Canon STM lenses are suitable for capturing video, as the noisy autofocus system won’t ruin the audio.

Types Of STM Lenses

Canon offers two main types of STM lenses.

The first Canon STM lens features helical gears to rotate the autofocus system. It tends to have a slow focusing performance. But on the upside, the gears take up less space in the lens body. As such, geared STM lenses are lighter and more compact than the next lens type.

Another STM lens uses a lead screw-type motor. It offers faster and quieter autofocusing than the gear-type STM. The only downside is its slightly larger and heavier construction.

Advantages of STM Lenses

The main advantage of using STM lenses is their silent performance. They rotate the motor in predetermined steps and stop after each movement. This way, they offer quiet performance without the constant whirring sound of other AF motors.

Another benefit of a stepping motor lens is its smooth movement. It can effectively prevent jerky motions when focusing on fast-moving subjects.

Finally, Canon STM lenses are relatively affordable. They are a great budget-friendly option for beginners who want a reliable autofocus system.

Disadvantages of STM Lenses

While STM lenses offer several benefits, they also have a few disadvantages to consider.

First, these lenses tend to be slow compared to other autofocusing systems. They are still faster than standard lenses, but they can lag behind when you need to capture fast action.

Although STM lenses are more suited for general video, they not be ideal for certain video recordings, such as sports and wildlife.

Some STM lenses may even have a limited aperture range. They can prevent you from capturing other types of photography.

What Is a USM Lens?

What Is a USM Lens

USM refers to ultrasonic motors in Canon lenses. A USM lens features this motor type to drive the autofocusing system. It offers incredibly fast performance because it makes use of the ultrasonic vibrations for energy. It is suitable for capturing action, sports, and wildlife photos.

Besides its fast focus speed, the USM lens also delivers accuracy. It can help you take incredibly sharp photos of fast-moving subjects like animals, cars, and more. It is the top choice of many professional photographers.

Types Of USM Lenses

USM lenses come in three main types.

A ring style USM lens has two rings—one connects to the autofocusing elements, while the other attaches to the barrel. The way it functions enables you to switch to full-time manual focusing with ease. How it works: to achieve focus, the first component starts to vibrate at an ultrasonic frequency. This movement causes the second ring to rotate and focus on the subject. 

Another type of USM lenses is the micro USM. Its motor doesn’t connect to the AF group elements. Instead, it features a geared motor driven by ultrasonic vibrations. It delivers fast focus, but it can also produce a lot of noise. It also lacks a manual focus option.

Finally, nano USM lenses offer high-speed autofocus and silent operation, ideal for sports and wildlife photography. They use the latest AF technology from Canon. However, they might be more expensive than the other two types. 

Advantages of USM Lenses

A USM lens relies on ultrasonic vibrations to drive the focus ring in the lens. It provides incredibly fast focusing speed, even quicker than STM lenses.

A lens with an ultrasonic motor also offers better manual focus override. This feature enables you to adjust the focus manually, even when the lens is in autofocus mode. There is no risk of damaging the internal AF group elements.

Finally, USM lenses have high-quality construction. They tend to be more durable and long-lasting than other types of Canon lenses.

Disadvantages of USM Lenses

The primary disadvantage of a USM lens is its noisy performance. It produces a whirring sound when moving the internal focusing elements. This noise is audible when you capture a video. That is why most filmmakers and videographers still use STM lenses, despite their slower autofocus performance.

A USM lens tends to be larger and heavier than its STM counterparts. It might not be the best lens to bring during travel or street photography.

Finally, USM lenses can be quite expensive because of their advanced focusing elements.

STM Lens vs. USM Lens: Key Differences Between Two Canon Lenses

STM and USM refer to the autofocus systems in most Canon lenses. Both AF lens systems deliver excellent results but function differently. 

Below, we will cover the five key differences between these two camera lenses.

Acronym Meaning

STM stands for stepping motor, while USM means ultrasonic motor.

STM lenses rotate the lens ring with the stepping motor. As its name suggests, this motor moves in steps to ensure smooth and silent operation.

On the other hand, USM lenses with ultrasonic motors deliver ultra-fast and accurate autofocus. 

If you see a camera lens without STM or USM markings, it likely has a direct drive motor. Also known as DC, this motor is common in old or budget-friendly Canon lenses. A DC lens is still a better option than traditional lenses without an AF system, but it is slower than STM and USM lenses. 

You might also encounter the IS II vs. STM lens debate. IS II simply denotes a second version of the lens. It has nothing to do with the autofocus system at all.

Manual Focus

The STM lens does not offer a manual focusing override. If you want to move the lens ring manually, you must wait for the AF elements to stop. Or you must press the shutter button halfway to enable manual focus on the autofocus lens. It is not a serious issue, but might be a hassle if you want to adjust the focus.

In contrast, a USM lens enables you to focus manually in a mechanical way. It even allows you to rotate the focus ring even when the camera and lens are off. It is ideal for shooting on low batteries because you can set the focus in advance before turning on the camera.

Focusing Speed

STM lenses have a quick autofocusing speed. However, they tend to struggle when you are shooting fast-moving subjects.

Meanwhile, Canon USM lenses can find focus in a fraction of a second. They have ultra-fast autofocus performance, ideal for action, wildlife, and sports photography.


STM lenses are silent because of the motor design. They stop rotating the lens ring every step, which reduces noise from the focusing mechanism.

Unfortunately, the same could not be said for USM lenses. They tend to produce a loud whirring sound every time they find focus. This noise can be audible and ruin the audio of the video you’re trying to capture.


STM lens is an older focusing system by Canon. It also has fewer elements and a more compact design. Hence, it tends to be more affordable than a USM lens.

A USM lens can be expensive because of its advanced focusing system. It is suitable for more professional photographers.

Which One is Better: STM Lens or USM Lens?

Choosing between a Canon STM and a USM lens depends on your needs, preferences, and budget.

Canon STM lenses are popular because they perform well with less lens noise. They are also fast enough to give you sharp images. Plus, they are more compact and affordable than most USM lenses. So if you are on a tight budget or prefer a silent lens, then choose a lens with a stepping motor.

Do you often shoot fast action, wildlife, and sports? Then, USM lenses might suit you better. These lenses use an ultrasonic motor to nail the focus in a fraction of a second. They also offer manual focus override to ensure accuracy. However, they tend to be louder and heavier. But if any of these things aren’t a concern, go ahead and buy USM lenses.


Shopping for a Canon camera lens can be overwhelming due to the various models and abbreviations. One of these is STM, which means stepping motor.

STM lenses use a stepping motor to move the focus ring. They offer smooth and silent autofocusing performance. They also come in different types and benefits, as we covered in this article.

Do you have more questions about Canon STM lenses? Feel free to send a message on our contact page, and we’ll get back to you soon.