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STM vs. USM
  
 
Herb
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p.1 #1 · p.1 #1 · STM vs. USM


I just watched a video by Canon on their STM technology in their lens. Is the plan to put STM in the L lens because it is quieter for video as well as does a nicer job locking into focus in a changing environment?

I am looking for an explanation into the logic of USM versus STM lens. Comments?



Jan 02, 2018 at 08:29 PM
johnctharp
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p.1 #2 · p.1 #2 · STM vs. USM


Herb wrote:
I just watched a video by Canon on their STM technology in their lens. Is the plan to put STM in the L lens because it is quieter for video as well as does a nicer job locking into focus in a changing environment?

I am looking for an explanation into the logic of USM versus STM lens. Comments?


Well, many USM implementations by Canon as well as those by Sigma and Tamron have been shown to be effective with Canon's DPAF technology on their consumer cameras as well as their Cinema EOS cameras, at least in terms of responsiveness and smoothness of focus pulls. Many are even fairly quiet.

Further, for most lens element arrangements, USM motors will remain the fastest possible solution- something that the 'L' designation implies.

However, newer STM designs have been shown to be relatively quick and are certainly quiet and smooth by default, so the possibility remains if a lens has a video (or mirrorless!) 'focus'.

One further development has been Canon's 'Nano-USM', which is a linear motor (magnet on a rail), and the implementation in the new 70-300 IS Nano-USM certainly checks nearly every box that would befit an 'L' lens; if the lens were more ruggedized and weather resistant, it might even stand in as a 70-300L replacement, though don't quote me on the point as to which has the fastest AF and best tracking on a 1D X II.

So there are a number of possibilities, but if I were to make a prediction, it'd be that Canon would work to continue to refine their ring USM motors for the purpose of smooth and quiet focus pulling for video usage while retaining the snappiest possible AF response for stills shooting with their premiere lenses. If I were to modify that prediction at all, it'd be that their 'second tier L' lenses, such as the f/4 zooms, might adopt STM or Nano-USM motors, but as both have been available while lenses such as the 24-105/4L II and 85/1.4L IS have been released and both with ring USM motors, I will rate that modification as unlikely .



Jan 02, 2018 at 09:09 PM
Gochugogi
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p.1 #3 · p.1 #3 · STM vs. USM


I have nano-USM on my 18-135 and it's smooth as silk for focus pulls but focuses faster than my STM optics for stills. I sort of expected nano-USM would replace STM but it doesn't seem to be happening. The latest crop of Dual pixel cameras focus very smoothly in movie servo with ring-USM lenses. I recall my 70D jerked and chirped like a bird when I engaged movie servo with most ring USM lenses. With my 80D and 6D2 those same USM lenses work pretty well for movie servo.


Jan 02, 2018 at 09:25 PM
Jeff Nolten
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p.1 #4 · p.1 #4 · STM vs. USM


Many if not all STM lenses lack full time manual focus. You have to put the lens in MF with the camera powered on to get it. I was comparing my 55-250 STM with a 500D closeup filter and the EF-S 60 USM macro. I found I could not prefocus the 55-250 near MFD and this would lead to a lot of hunting. The 60 was much easier to deal with in this situation.


Jan 02, 2018 at 09:28 PM
johnctharp
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p.1 #5 · p.1 #5 · STM vs. USM


Gochugogi wrote:
I have nano-USM on my 18-135 and it's smooth as silk for focus pulls but focuses faster than my STM optics for stills. I sort of expected nano-USM would replace STM but it doesn't seem to be happening. The latest crop of Dual pixel cameras focus very smoothly in movie servo with ring-USM lenses. I recall my 70D jerked and chirped like a bird when I engaged movie servo with most ring USM lenses. With my 80D and 6D2 those same USM lenses work pretty well for movie servo.


Yup, the IS USM WA trio (24/2.8 IS, 28/2.8 IS, 35/2 IS, I have the first and last) all behaved this way, apparently. They're also all well-behaved on current implementations.

And while I was aware of the Nano-USM in the latest EF-S 18-135, I wasn't sure if it was an example of a faster focusing lens like the 70-300 IS Nano-USM- great to hear that it is!



Jan 02, 2018 at 09:29 PM
johnctharp
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p.1 #6 · p.1 #6 · STM vs. USM


Jeff Nolten wrote:
Many if not all STM lenses lack full time manual focus. You have to put the lens in MF with the camera powered on to get it. I was comparing my 55-250 STM with a 500D closeup filter and the EF-S 60 USM macro. I found I could not prefocus the 55-250 near MFD and this would lead to a lot of hunting. The 60 was much easier to deal with in this situation.


To dial the point in here a bit more: they do most certainly have the capability for full-time manual focus and manual focus override, but as noted, this is controlled by the camera more than by the lens (depending on camera and lens combination; for the EOS-M cameras and EF-M lenses, it's all on the camera as far as I've seen).

For pre-focusing or focusing in the dark, this is most certainly a real-world limitation. It's probably why the dedicated EF-S and EF-M STM macro lenses have shipped with built-in lighting!


(and for real macro work, I'd just as well get a manual lens and focus by camera... Samyang's current model looks nice enough )



Jan 02, 2018 at 09:32 PM
R.H. Johnson
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p.1 #7 · p.1 #7 · STM vs. USM


what is the reliability and life time expectancy of usm vs micro usm vs stm technologies, while considering environmental performance? from an engineering perspective one would rather have reliability longevity environmental performance and stability in L glass vs technical enhancements with a decrease in lifespan.

just food for thought. this would be an interesting analysis. however, this is above my pay grade now that i'm a retired engineer.



Jan 02, 2018 at 10:10 PM
johnctharp
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p.1 #8 · p.1 #8 · STM vs. USM


I'd expect ring USM to be more robust, however, given that STM is a focus-by-wire technology by design, I'd have to say that we'll have to wait and see.

Except for those STM lenses with unit-focusing and/or extending designs like the budget oriented STM pancakes (22/2, 24/2.8, 40/2.8), and the 50/1.8 STM, all of which expose the STM motor when extended for focusing closer than infinity.

I'll also say that I own/have owned two of the pancakes as well as the 50/1.8 STM, and I haven't encountered problems, even with less than gentle handling.



Jan 02, 2018 at 11:34 PM
Gochugogi
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p.1 #9 · p.1 #9 · STM vs. USM


For some reason, FTM for STM had to be enabled in the freakin' menus on my 6D2. Seems strange to disable it by default. I do prefer the FTM implementation of ring-USM for my shooting style.


Jan 03, 2018 at 12:34 AM
 

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rolsen
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p.1 #10 · p.1 #10 · STM vs. USM


Jeff Nolten wrote:
Many if not all STM lenses lack full time manual focus. You have to put the lens in MF with the camera powered on to get it. I was comparing my 55-250 STM with a 500D closeup filter and the EF-S 60 USM macro. I found I could not prefocus the 55-250 near MFD and this would lead to a lot of hunting. The 60 was much easier to deal with in this situation.


This might be dum question, but did you remember to activate the focusing in camera before turning the focusing ring? IIRC at least my 24/40/50 STM lenses need the focus activation before you can manually override the focus (I have the AF in back button and lenses are always in AF mode).



Jan 03, 2018 at 09:17 AM
charlyw
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p.1 #11 · p.1 #11 · STM vs. USM


One reason why probably the L lenses will not get a Nano USM or a STM focusing motor is the weight of the focusing group in those fast lenses. Both these new focusing motors can only deal with rather light weight focusing groups.


Jan 03, 2018 at 03:14 PM
Jeff Nolten
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p.1 #12 · p.1 #12 · STM vs. USM


rolsen wrote:
This might be dum question, but did you remember to activate the focusing in camera before turning the focusing ring? IIRC at least my 24/40/50 STM lenses need the focus activation before you can manually override the focus (I have the AF in back button and lenses are always in AF mode).


Fascinating! My comment was using the 55-250 STM on my SL2. The focus ring is inoperative with autofocus switched on, I just retested it. I also tried it on my 80D and the focus ring works with AF switched on. So its camera body dependent or my SL2 has an issue.



Jan 03, 2018 at 08:20 PM
rolsen
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p.1 #13 · p.1 #13 · STM vs. USM


Jeff Nolten wrote:
Fascinating! My comment was using the 55-250 STM on my SL2. The focus ring is inoperative with autofocus switched on, I just retested it. I also tried it on my 80D and the focus ring works with AF switched on. So its camera body dependent or my SL2 has an issue.


Mmmkay, that sounds interesting. I have 7DmkII and 80D and both work similarly with STM lenses. I'm sure there are some members with SL2 and some STM lenses to try to reproduce this. Design or fault, cannot be sure.



Jan 04, 2018 at 01:34 PM
Jeff Nolten
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p.1 #14 · p.1 #14 · STM vs. USM


My SL2 behaves the same with the 10-18 and 35 macro STMs. Do hope we get some independent confirmation. My SL2 is still within its warranty period unless this is a feature.

Edit: I think my SL2's behavior demonstrates that the focus ring on STM lenses communicates with the camera which then instructs the lens' focus system, i.e. there is no direct link between the ring and the focus system.

Edited on Jan 04, 2018 at 05:34 PM · View previous versions



Jan 04, 2018 at 05:26 PM
molson
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p.1 #15 · p.1 #15 · STM vs. USM


Herb wrote:
I just watched a video by Canon on their STM technology in their lens. Is the plan to put STM in the L lens because it is quieter for video as well as does a nicer job locking into focus in a changing environment?

I am looking for an explanation into the logic of USM versus STM lens. Comments?


I assume this is a cost-saving move by Canon since STM lenses are focus-by-wire, which allows them to be made smaller and assembled more cheaply.

I think they need to do this to compete in the mirrorless niche, but I hope they never add this to the L-lenses (unless it's for new TS-E lenses, where it could be a benefit...)



Jan 04, 2018 at 05:27 PM
Gochugogi
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p.1 #16 · p.1 #16 · STM vs. USM


Jeff, I just tried my wife's SL1 and 55-250 STM and the MF feature works perfectly in AF mode. Just as long as I half-press the shutter button I can MF first or touch up after AF. Odd that the SL2 doesn't work that way.


Jan 04, 2018 at 06:51 PM
jcolwell
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p.1 #17 · p.1 #17 · STM vs. USM


I just tried my SL2 + 55-250 IS STM. With the lens switch on AF, and SL2 camera_menu_1 "Lens electronic MF = ON", MF works to adjust the focus, after focus is achieved using AF.

The MF adjustment only works when you still have the shutter half-depressed, from the original AF-setting half-push. IOW, if you half-push the shutter to achieve AF, then release the shutter button, and then rotate the MF ring on the lens, nothing will happen; it will not MF. OTOH, if you half-press the shutter to achive AF and rotate the MF ring (before releasing the shutter button), it will MF to adjust focus that had been achieved with AF.

I can try other stuff or provide more details, but we're just about to get weather-bombed, and so I might be offline for a while.



Jan 04, 2018 at 07:00 PM
Jeff Nolten
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p.1 #18 · p.1 #18 · STM vs. USM


Ah, thank you both! Mystery solved, internal setting. I'll have to adjust that. Yup, fixed, thanks. Much better for close focus work.


Jan 04, 2018 at 07:45 PM







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