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.

HWM (Malaysia) - - CONTENTS - By Zachary Chan

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.”

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