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-   -   STM vs USM (http://photocamel.com/forum/canon/175525-stm-vs-usm.html)

Surfwooder 01-01-2013 12:58 PM

STM vs USM
 
I have been looking at buying a new lens from Canon. My focus is on the 18-135mm size lens. I notice this lens comes in a USM type focus, and STM focus motor. I know the names of these motors (ultra-sonic motor, and stepping motor) but, if any, what advantage, or disadvantage do this two different motors have on the function of the lens. I own the Canon EF 40mm STM, pancake lens, it has a STM it focuses fast enough, but there is nothing to compare it with.

Gene243 01-01-2013 01:26 PM

Re: STM vs USM
 
STM is the new technology if your camera will support it it's brobably better than the old type. It has better immage stabilization than the old USM.

Surfwooder 01-01-2013 02:06 PM

Re: STM vs USM
 
After reading your response, I can only wonder why the new technology is not present in the Canon "L" lenses. I'm thinking the STM may be more responsive than the USM system. I have no data to support this thought though.

ron_o 01-01-2013 02:38 PM

Re: STM vs USM
 
I researched this a while back, STM lenses are designed to be for video shooting. They are quieter and ease into the focus smoother and don't "hunt" for focus like a USM lens sometimes will. STM is a brush less motor.

STM and USM refer to the focusing motors and not the IS motors.

swampler 01-01-2013 02:43 PM

Re: STM vs USM
 
Quote:

Originally Posted by ron_o (Post 1783021)
I researched this a while back, STM lenses are designed to be for video shooting. They are quieter and ease into the focus smoother and don't "hunt" for focus like a USM lens sometimes will. STM is a brush less motor.

STM and USM refer to the focusing motors and not the IS motors.

+1

FrodeS 01-01-2013 03:00 PM

Re: STM vs USM
 
My oldest daughter has the 18-135mm STM on her 650D - as she mostly makes films with her DSLR, it is perfect - the lens is focusing very quiet. And the active AF while filming backs it up nicely.

I gave it a whirl just now with some stills, and I feel like the STM focuses slower than the USM on my lenses - I have done no research into this; but it is based on my experience test-shooting at home now.

Mind you - the usm lenses (ring type) tested are both L lenses so price wise it is probably not a fair comparison.

The build quality and sharpness on my daughters 18-135mm STM was surprisingly good and manual-focus override was an added bonus as well! :-)

Surfwooder 01-01-2013 03:38 PM

Re: STM vs USM
 
So far as I see it, the STM focus motor will follow the focus of the subject quieter, but not faster even when focusing during the movie mode. I shoot with a 50D, that will not make movies. I guess I would see a difference when using Al Servo mode.

Naturalist 01-01-2013 03:51 PM

Re: STM vs USM
 
From my reading the Canon website I think the STM lenses are quieter and more responsive for when you are shooting video with your DLSR so less noise in introduced into your video.

Canon U.S.A. About Canon
New STM Lenses and Accessories To leverage the unique, new shooting functions of the EOS Rebel T4i, such as EOS Full HD Movie with continuous AF, Canon is introducing two new unique lenses, the new EF-S 18-135mm f/3.5-5.6 IS STM lens and new EF 40mm f/2.8 STM lens. Both new STM lenses includes Canon's new Stepping Motor technology, which allows the lenses to smoothly and silently focus, and when used in combination with Canon's new EOS Rebel T4i Movie Servo AF feature, achieve continuous AF while recording video. The versatile EF-S 18-135mm f/3.5-5.6 IS STM lens offers the right combination of size, weight, image stabilization and focal length, allowing photographers to capture wide-angle or telephoto photographs and video. The new EF 40mm f/2.8 STM lens offers an ultra-slim, lightweight design that helps photographers avoid overwhelming their subjects with a large lens and to remain discreet in sensitive shooting situations without compromising performance.

scoundrel1728 01-01-2013 07:44 PM

Re: STM vs USM
 
I thought one of the big features of USM focusing was both its speed and quietness - quietness to human ears anyway. Ultrasonic motors operate so fast that most of their acoustical noise is too high-pitched for humans (or most microphones) to hear. I've designed using stepping motors before. The whirring sound you hear in robotic arms and other appendages is from stepping motors. I find it hard to believe that they would be quieter than ultrasonic motors unless they can also be made to operate at ultrasonic frequency.

scatterbrained 01-01-2013 08:59 PM

Re: STM vs USM
 
STM is not "quieter" than USM. It is quieter than the linear DC motor driven lenses like the 15mm 2.8. If you've used on of the non usm lenses, it's quite loud. As far as USM, there's USM, and then there's the ring type USM found in the higher end lenses. They are not the same. The ring USM found in L lenses is both quieter and faster than STM, but STM is somewhat better in performance than the older type of USM found in the consumer/entry level lenses.


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