On many Canon lenses, you’ll either find STM or USM written which specifies the kind of motor that the lens uses for focusing. In this post, we’ll be talking about the difference between STM lenses and USM lenses.
We’ll also see whether an STM lens or a USM lens is a better fit for your photography.
STM lenses use a stepping motor, which is a very smooth but slightly slower by way of autofocusing.
USM lenses use an ultrasonic motor, and they are faster than STM lenses.
- The “Skew” and “Distort” both are options to transform and constrain your design.
- You can distort the image while maintaining the original proportion.
Originally, autofocus systems were operated using an autofocus motor that sat in the body of the camera rather than in the lens. A mechanical gear would connect the motor to the lens, and the motor inside the camera would rotate the lens to achieve a desired focus.
Back then, there were plenty of big camera manufacturers: Canon, Nikon, Yashica, and Pentax. Of these 4, Nikon, Yashica, and Pentax used a similar design to keep the motor in the camera body.
Canon designers decided to try another method by putting the motor in the lens. As it turns out, Canon’s designers hit the nail on the head and their system was far superior to the others.
Eventually, everyone else switched to a system based on Canon’s(with their own tweaks, of course).
Canon lenses today use one of three kinds of motors: a STM motor, a USM motor, or a regular DC motor.
Canon STM vs USM Lenses
DC or direct drive motors
Even though most Canon lenses have STM or USM motors, if your lens does not specify it, it probably has a DC motor. a DC motor is the bottom of the pile in motors: there’s no smoothness of STM, no speed of USM, but it can do the job and as a budding photographer, it may not matter to you.
What are Canon USM Lenses?
USM stands for Ultra Sonic Motor.
The ultrasonic motor is the most popular kind of motor for autofocus lenses and most Canon lenses have an ultrasonic motor powering the focus mechanism. In Canon USM lenses, ultrasonic vibrations are converted into rotational energy which is used to move the lens. For this to work, you need two loosely coupled rings. By vibrating one of the lenses, the other will rotate.
One ring is on the body, and the other ring is on the focusing part of the lens. USM motors have the advantage of speed. If you need to click really fast, the USM motor can keep up really well. You can also make small manual adjustments without having to turn autofocus off.
Ring USM lenses
Even USM motors are of a few different types! Ring USM motors are the most common variation of autofocus motors in USM lenses.
The motor itself is quite powerful and allows for a level of exact precision. You don’t need any mechanisms to reduce the speed of the motor. Additionally, once the motor has found a good position, you don’t need to keep applying power to it to maintain that position.
They are also very responsive, and it’s no surprise that Ring USM motors are the most common kind of motor found in Canon lenses.
Micro USM lenses
Micro USM – as the name suggests – is a much smaller motor so it can fit into much smaller lenses. These are also cheaper so where micro USM motors are used, the price of the lens is less as well.
Micro USM uses a motor similar to the regular USM motor, but in this case, it’s not directly connected to the focusing rings. Instead, gears are used which actually makes it a hybrid between an old school autofocus system and the newer USM system.
Nano USM lens
Canon’s latest development is Nano USM lenses, which have a high speed autofocus mechanism that is just as good as the regular USM lenses and just as quiet and smooth. It’s probably the best kind of lens to use for everyday photography and even video.
You can shoot good, smooth video in which your camera focus keeps up with your moving subjects. Of course, it will shoot really good photographs, too.
Why you should use USM lenses
USM lenses are very fast. If you’re shooting fast-moving subjects and moving your camera back and forth, you don’t want to waste any time manual focusing or waiting for the camera to focus. You need the camera to focus very fast so you can capture your subject!
The disadvantage to USM lenses is that there is a lot of lens noise. If you shoot video, most of the audio picked up by the microphone will be the whirring and clicking of your USM lens.
Ring type USM lenses let you disable the autofocus motor and let you take control with manual focus. Here, you can turn the focus ring and do as you please with your shot.
The best of the best in USM lens technology is the Nano USM lens, which is as quiet as a stepper motor lens and has all the speed of USM.
What are Canon STM lenses
STM motors as you read above are smoother and quieter than USM motors. If you’re looking to shoot videos as well as photos, you can’t go wrong with a lens that uses STM motors.
Because it’s so quiet, your microphone won’t pick up any of the internal noises in the camera and you’ll be able to capture more of the actual subject’s sounds.
Stepping motors are called stepping(or stepper) motors because they can execute very tiny movements down to 0.1mm, and they can do them really fast. In fact, stepper motors are used in 3D printers for this very reason.
The small and precise movements are ideal for keeping up with the constantly changing focal length required when shooting videos.
This system is totally electronic and there are no gears or rings involved.
Smaller lenses using STM motors use gears to change the focus.
Lead-screw motors are used in larger lenses(where you have more space). Lead screw motors are even more quieter and can achieve faster speeds than gear STMs.
Why you should use STM lenses
STM lenses have a focus ring that does not make any noise. As a result, STM lenses tend to be much quieter than their USM counterparts, making them ideal for video.
The focus is fast, but not as fast as a USM lens.
Another advantage of the Canon STM autofocus system is that STM lenses are much cheaper than USM lenses, so if budget is an issue, stick to Canon STM.
Canon STM vs USM: Which one should you get?
For professional applications and for shooting higher quality photographs, USM lenses remain the undoubted champion of professional grade lenses.
For amateur photographers who also shoot lots of video, STM lenses shine – they’re totally silent and can deliver really crisp video. The focus speed is a bit slower but that allows for more smoothness.
Ultimately, there’s no “one” answer as to which Canon lens you should or should not use. Both types of lenses let you take over for manual focus, and the image quality will be the same in both an STM lens and a USM lens.
If you’d like to stick with USM lenses for video, one way to get around the motor noise is to not use the camera’s microphone and instead use a boom mic or a lapel mic to record audio.
Finally, whether you choose STM vs USM, you’re not married to a particular type of lens. As you grow as a photographer, you will find yourself buying more lenses and growing your collection of photography gear!