If you’ve shopped for Canon lenses, you might have noticed the terms STM and USM thrown around. They refer to the motor mechanism behind the lens’ autofocus. USM uses ultrasonic vibrations to turn the focus ring, while STM uses gears.
I’m Caleb, and I’ve been a photographer for more than four years. During that time, I’ve gotten pretty familiar with Canon lenses as a user of the Rebel T7i.
In this article, I break down the differences between USM and STM lenses and explain the best uses for each.
If you want to know more, and hear my advice on which one to buy, keep reading.
What’s the Difference Between USM and STM?
STM and USM are both terms that have to do with the autofocus feature. STM stands for stepping motor, while USM stands for ultrasonic motor. The difference lies in the way each one works.
When you have autofocus turned on, the focus ring moves by itself after you press down on the shutter button. USM and STM are separate ways to make that happen. USM lenses use tiny vibrations to move the focus ring into the correct place, while STM ones use gears.
But the differences aren’t just in how these lenses work. USM lenses usually focus quicker, but this comes at the expense of making more noise than their counterparts. STM lenses are quieter, but slower to get into focus.
STM vs USM: Which Is Better?
There’s no objective answer when comparing which of the two lens types is the best. USM lenses are considered better for still photography, and STM lenses for shooting video.
The difference in role stems from the noise factor. STM lenses are much quieter, which is a need for some videographers. In a video like a vlog or a documentary, the last thing the audience wants to hear is the noise from a camera lens distracting from the intended focus.
With still photography, on the other hand, this usually isn’t a concern. There are also plenty of situations in still photography where getting the subject in focus quickly is a big advantage.
In sports photography, for example, you might only have a few seconds to focus on the subject and take the picture before the moment is over. And when photographing animals, waiting too long might result in the subject moving away.
However, performance isn’t the only thing to consider before choosing between these two lens types. There’s also cost. USM lenses trend towards the more expensive side, so you’re more likely to see them in the hands of professional photographers.
If you’re a newer photographer, you should ask yourself whether you really need the added speed of a USM lens.
At this stage, it’s probably more important for you to learn photography fundamentals. An expensive lens isn’t that great of an investment if you don’t know how to get the most out of its high-end specs.
Why Are USM Lenses More Expensive?
It’s mainly because USM and STM lenses are targeted at two different audiences. This can be seen in the build quality of USM lenses, as they are generally heavier and better protected against the elements.
Also, USM technology is used in Canon’s L Series lenses. The L in this series stands for ‘Luxury,’ and these lenses are more expensive and have features that aren’t present in Canon’s cheaper models.
Almost all of them make use of USM motors, and none of them use STM. We can see from this that Canon associates USM with their higher-end products.
What Are DC Motors?
You may have noticed that some Canon lenses aren’t marketed as USM or STM. These lenses use the older DC motors, also known as direct drive.
This is the technology that Canon used before the introduction of USM and STM lenses, and you can expect an absence of the benefits from the newer lenses.
DC lenses don’t have the faster speed or the lower noise level of their counterparts, so you should be mindful if you’re thinking of buying a lens that lacks either USM or STM in the title.
Here are a couple of other related questions that came up surrounding Canon’s lenses.
Are STM Lenses Good for Photography?
STM lenses can still be used for still photography, even if their strongest area is recording video. However, they aren’t as good as their USM counterparts when quick focus is needed.
What is the Difference Between USM and HSM?
HSM lenses offer the same thing as USM lenses. However, HSM lenses are produced by Sigma while USM lenses are made by Canon.
As a general rule, USM is the higher-end of the two motor options provided for Canon lenses. But it’s not the best for every situation, and in some cases such as shooting video, STM has more advantages.
The best option for you will depend on your needs and how much money you’re willing to spend on a lens.
Do you have a preference between one lens type or the other? Or are you on the fence about which one to buy? Tell us about it in the comments.