# Is the 5D3 compatible with STM lenses (e.g., new 40mm f/2.8)



## fotoray (Jul 17, 2012)

My understanding is that STM lenses offer quieter focusing for video and the new T4i is apparently compatible with STM lenses for this purpose. Is this also true for the 5D3? The 5D3 user's manual makes no mention of STM. If 5D3 not compatible, can firmware update make it compatible?


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## RLPhoto (Jul 17, 2012)

Yes. :


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## victorwol (Jul 17, 2012)

fotoray said:


> My understanding is that STM lenses offer quieter focusing for video and the new T4i is apparently compatible with STM lenses for this purpose. Is this also true for the 5D3? The 5D3 user's manual makes no mention of STM. If 5D3 not compatible, can firmware update make it compatible?



Well... Compatible is because can be used. But there is no real autofocus on the 5D MKIII in video mode, not the kind you have on the t4i. And I have read it will not happen.


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## Mt Spokane Photography (Jul 17, 2012)

The T4i is the first body to take advantage of the STM, but it works very well on all older models, but there are some additional things using them with a T4i brings.
Autofocus during video only applies to the T4i, and even then, its not a camcorder, its crude. My D800 would autofocus during video as well, but it was really struggling.


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## takoman46 (Jul 17, 2012)

I didn't read too much into the STM but my understanding was that they facilitated continuous auto focusing while recording video with the T4i. The 5D Mark 3 is not equipped with continuous auto focus while recording video so I don't think an STM will be beneficial. Also, if the STM lenses are supposed to be known for quiet auto focus, are they being compared to non-USM or ring USM lenses? I don't know how much quieter you can get than a ring USM lens so maybe they are comparing the STM to the non USM lenses? Anyway, my take on continuous auto focus is that it is intended for casual shooting since any auto focus system is not accurate enough for pinpoint focusing of shallow DOF lenses. Any auto focus system will still hunt in video mode and miss focus so don't expect it to function like it has an advanced AI built in. Learn manual focus for video if you need fast and accurate focus.


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## mb66energy (Jul 17, 2012)

fotoray said:


> My understanding is that STM lenses offer quieter focusing for video and the new T4i is apparently compatible with STM lenses for this purpose. Is this also true for the 5D3? The 5D3 user's manual makes no mention of STM. If 5D3 not compatible, can firmware update make it compatible?



STM lenses (I own just the shorty 40) can be focused without audible noise if - and that's the point - you turn the focus control ring SLOWLY. If you move it fast you hear the typical sound of stepper motors well known from ink jet printers.

I think that the different technologies are well separated by their properties:

Gear motors (like old 2.8/24): Fast, speed is moderately controllable. Substantial noise emissions.
USM: Very fast, speed is moderately controllable, very low noise emission (noise of fast moving mechanical components, not the drive itself),
STM: Acceptable speed, speed control is excellent (by performing the required steps per time interval), position control is excellent (like in ink jet printers), nearly noise free in "slow mode" - where the noise of mechanical elements is minimal

I do not own the 650D so I have no experience about its video mode - but on a 40D you can focus the lens noiseless by turning the focus control ring very slowly. I think that the video AF system of the 650D will use that slow speed to bring objects/subjects during video in focus. Not only to avoid noise but also to avoid to harsh focus changes. If you want to pull the focus fastly between two extremes - person in front and landscape behind - you will hear the ink jet printer-like noise with the shorty 40.

In my opinion the new entry level full frame will have an on-chip-phase-detect AF system to achieve the full STM compatibility - let's see the 650D as a forerunner which tests the system in the field. And the full frame system will adjusted according to these experiences.
O.k., some say, AF is not necessary in video - but I see a lot of applications for spontaneous interviews oder documentations. And if the new full frame camera is an entry level system it is intended for a lot of people who are not primarily videographers but interested in using it. If the first tests with video are satisfying - people will expand the use of video and their capabilities ... and by further STM lenses, camera bodies, etc. ... and lern to focus manually for some situations.


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## Abraxx (Jul 17, 2012)

At this point in time, these are my findings regarding STM:
- slower focus than USM
- continous AF possibly in video, but not really smooth, compared to a little training and doing it manually
- lower noise, but still noise audible when using continuos AF, manual is still better for STM when noise is crucial
- good for ad hoc AF videos or travel videos, so at the current stage I do not think its of interest for pro video but rather for entry level (which does not mean, that we don't see STM capability on an entry FF in the future)

I personally do not think we'll see a L lense with STM anytime soon, for my taste, normal focus is noticably slower with STM than USM (non video). I believe though that Canon will add these feature to all future Cams...
A pity that they did not introduce it with the 5D3 already


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