What is Nano USM and why should it matter when choosing a zoom lens?
Canon’s engineers came up with a way to make lenses lighter and more precise, literally by making its components much smaller, and functionally too, because you now only need one zoom lens for both stills and video. Here’s how the magic works.
WHAT’S IN A NAME?
We’re normally more caught up in the advances made to a camera body than the lenses that accompany it, and rightly so, because that’s where all the megapixels, varied autofocuses, and image processors are all located after all. What about lenses then? Are they just the sum of their focal lengths and aperture ratings?
Take Canon’s standard EF-S 18135mm zoom lens, for example. There have been multiple versions of this lens, the EF-S 18-135mm f/3.5-5.6 IS from 2009, the EF-S 18-135mm f/3.5-5.6 IS STM released in 2012, and the EF-S 18-135mm f/3.5-5.6 IS USM released in 2016. You’ll notice that all three lenses have exactly the same optical specifications; 18-135mm telephoto length and f/3.5-5.6 aperture. All three lenses have image stabilization, as indicated by the IS designation.
What’s actually different about these lenses is the mechanism that drives the lens elements during autofocus as you’re shooting. The original lens uses a more traditional micro motor to drive its focusing. As videography became more prominent among DSLR uses, the second lens with a new Stepping Motor (STM) was introduced. STM achieved two things: silent and smooth AF operation while shooting video. However, while STM was great for videography, it wasn’t quite capable of keeping up with the speeds required by modern highspeed phase detect AF systems, such as Canon’s own Dual Pixel CMOS AF.
ENTER NANO USM
The term USM stands for UltraSonic Motor, and there are actually three different types of USM implementations. The first two—Ring USM and Micro USM—drive the lens through rotational movement, and can be found in heavier and professional range of Canon lenses specifically designed for high-speed photography. These are not the focus of this article.
Nano USM is the latest and smallest iteration of this technology. It is
also the first to marry the speed and responsiveness of USM for still photography, and STM for smooth and silent videography.
HOW DOES IT WORK?
The motor itself is so tiny, it fits on the tip of your finger. The Nano USM component is actually a combination of a ceramic piezoelectric element and an elastic metal body. When current is applied to the element, the body flexes and changes shape. Depending on the type and rate of the current applied, precise control of the flexing is achievable, generating the high-speed ultrasonic vibrations required to move the lens elements, which in turn results in incredibly quick and responsive focusing.
Unlike the Ring- and Micro-type USM implementations, Nano USM uses a linear drive similar to STM. In fact, they’re basically the same in principle. Both implementations use a guide bar to move the focal lens in a straightline motion.
In the STM implementation, actuation is achieved using a leadtype screw and rack assembly driven by a stepping motor. The stepping motor functions using pulse signals to drive small minute movements, which translates to a silent, smooth, and continuous AF that’s required for videography. But, as mentioned before, STM is unable to match USM in terms of driving speed and responsiveness.
The Nano USM implementation replaces the entire mechanical stepping motor, lead-type screw, and rack assembly of a traditional STM, leaving just the Nano USM itself to drive the focal lens along the guide bar. Not only does this reduce the complexity of the lens assembly, it also helps to reduce size and weight of the entire lens.
This is why Nano USM-equipped lenses, such as the EF-S 18-135mm f/3.5-5.6 IS USM and EF 70-300mm f/4-5.6 IS II USM, are ideal for any situation, be it high-speed, highprecision AF for still photography, or quiet and smooth AF for videography.
“NANO USM TAKES THE BEST OF BOTH USM AND STM TO MAKE THE IDEAL LENS FOR STILLS AND VIDEO.”