Canon is well known for it’s high performance autofocus lenses. In this article you will find the difference between Canon’s STM and USM systems.
The big picture difference is the older USM (Ultrasonic Motor) system places an emphasis on speed and accuracy while the later produced STM (Stepping Motor) system was designed for silent operation.
STM VS USM Background
Original autofocus systems for digital cameras were housed within the camera. These systems were used by all major camera brands and worked under the a similar design. A mechanism that was like a screwdriver was used to focus the image.
Canon was the first major camera manufacturer to start putting the autofocus system within the lens itself. The first in lens autofocus system Canon produced was the EOS (Electro Optical System). The EOS utilized a DC motor that powered a gear train that wrapped around the optical cell of the lens.
Canon also developed a piezoelectric ring motor that could function without a gearbox.
These early lens autofocus systems paved the way for the ultra fast USM autofocus systems that are widely popular today.
Current Types of Canon Focusing Motor
Today’s Canon lenses offer three types of focusing motors. The STM, USM and the older DC motor. Here are the differences between these three motors. Understanding how they operate and what they are designed for will allow you to pick the best type for your photography style.
- USM: Ultrasonic Motor
The USM system was first released to the public by Canon in the 1990’s. Canon’s USM autofocus system is the most widely used system in the world. They function by converting ultrasonic vibration energy into rotational force that moves the lens in order to focus. The theory behind the development of the USM lens is that certain vibrations apply to one of the two coupled rings in the lens which causes them to rotate. One of these rings are attached to the body of the lens and the other is attached to the autofocus group.
The USM motor is the fastest autofocusing system Canon offers. It also allows you to manually set your focus for more control over your focusing.
Ring Type USM: This is the most widely used USM type for Canon EF type lenses. They offer power that drives the focusing group quickly without the need for an internal gear system. And when the motor is off they maintain holding power so the lens remains in focus. They start and stop quick for the fastest focus response time in the Canon family.
Here is a complete list of the current lenses using the USM ring type focusing system
Micro USM: The micro USM motor is another widely used AF system. It is small enough to fit in the barrel of all Canon lenses. The micro motor of the USM system is cost effective and is found in most lower priced lenses. It utilizes a similar sonic vibration motor to that found in the ring type. The difference is that it uses a series of gears which is more similar to the traditional AF systems. This means that there is more noise as the gears are not silent.
Here is the complete list of Micro USM Canon lenses
|Micro USM||Micro USM II|
|EF50 f/1.4 USM||EF28-105mm f/4-5.6 USM|
|EF28-200mm f/3.5-5.6 USM||EF S18 55mm f/3.5-5.6 II USM|
|EF55-200mm f/4.5-5.6 II USM|
|EF70-300mm f/4-5.6 IS USM|
|EF75-300mm f/4.5-5.6 III USM|
Nano USM: This system was produced in 2016 and it’s performance is on par with the ring USM while being silent and smooth. The Nano USM system is one of Canon’s most sophisticated and popular due to this great performance. They are great for still shots and video capture.
In effect, the nano combines the performance of the ring type with the silence of the STM system. This makes them great for shooting video and action stills.
One of the most popular Nano AF lenses is the Canon EF-S 18-135mm f/3.5-5.6 IS USM. It offers exceptionally smooth and fast autofocus.
With the Nano system you get amazing control and subject tracking even when they are moving fast.
2. STM Stepping Motor: The STM is an awesome AF system perfect for shooting still shots and video. The stepping motor allows for smooth fast and silent focusing. This makes it particularly well suited for shooting video and action stills. When shooting video, the silent AF allows you to capture the real world sounds of your scene better than you can with a loud AF. The STM Canon lens line offers a wide selection of high quality options for all types of photography.
The stepping motor does a great job at producing ultra smooth incremental focusing movements. This allows for contrast detect AF. The only negative to the STM system is that lenses are focus by wire. This means that the focus ring is not attached to the mechanism. This system instead sends a signal to the motor electronically in order to change the focus position. The real world effects of this is that you will lose the tactile connection of more traditional AF systems.
Gear Type STM: These lenses are compact and offer a gear type STM system. The gears drive the focus system.
Lead Screw Type STM: This system features a larger line of lenses that use the lead screw type over a gear driven focus.
|EF 40mm f/2.8 STM||EF S 55-250mm f/4-5.6 IS STM|
|EF S 10-18mm f/4.5-5.6 IS STM||EF 24-105mm f/3.5-5.6 IS STM|
|EF 50mm f/1.8 STM||EF M 55-200mm f/4.5-6.3 IS STM|
|EF M 11-22mm f/4.5-5.6 IS STM||EF M 15-45mm f/3.5-6.3 IS STM|
When looking at the difference between USM and STM lenses remember that USM lenses are the professional grade line while the STM lenses are designed for beginners and video capture. The STM system is nearly silent and are best suited for shooting video. They offer a slightly slower focus speed while the USM system is perfect for fast and smooth still photography shooting.
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- Best Canon Rebel XSi Lens
- Best Canon Lens for Portraits
|Ultrasonic Motor Autofocus||Stepping Motor Autofocus|
|Higher Cost||More Affordable|
|Professional||Amateur and Video|
|Best Still Shot Focus||Best For Video Capture|
|Motor less silent||Silent motor|
|Fastest focus speed||Slightly slower focus speed|
|Canon L Series|
|Great build quality and weather seal|