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There are incredible reviews on the new Canon STM lenses:

https://www.youtube.com/watch?v=ho0hOhRSuHk

Does autofocus perform better on a 7D body, compared to an entry-level 700D body, for example? There seems to be reviews that go in that direction:

https://www.youtube.com/watch?v=hBgYg4e6BYE

Which body would best fit an STM lens, then?

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interesting additional reading the-digital-picture.com/Photography-Tips/… –  dav1dsm1th Jun 11 at 22:59
    
You need to define exactly what you mean by "better". Speed? Accuracy? Shot to shot deviation? Audible noise? Smoothness/hunting? Etc. –  Michael Clark Jun 12 at 1:10
    
I agree with Michael, but based on the text of the question and the content of the video you link, I'm assuming you mean autofocus performance. Please re-edit if this guess is wrong. –  mattdm Jun 12 at 2:16
    
Hi, sorry for not being 100% clear in my question: I was talking about the smoothness and speed of the autofocus. I'm no photography expert, but I could imagine this is an effect of both the lens and body, what @Hugo confirmed in his answer. Thanks! –  plang Jun 12 at 9:11
1  
I'm disappointed with the 1st video you link above - on the non-hybrid AF camera they say the STM lens "focuses instantly" and "the non-STM is a little slower", when the times are 3.09s vs 3.17s. Those are virtually indistinguishable. Also, they're talking about Live View AF - none of this matters for using the old-fashioned (standard) optical view finder. If live view & movies are what you're about, that's great, but otherwise I think this is a basically just marketing material. –  khedron Jun 12 at 16:32

2 Answers 2

up vote 2 down vote accepted

The focus speed of a DSLR system depends on both the lens and body. The same lens can have different AF performance depending on body used.

The autofocus system on the 7D is considerably more advanced than that of the 700D and I would expect it to reflect the overall autofocus performance of the system.

In general STM lenses have an advantage compared to USM lenses when using contrast detection autofocus. You can read more about that here. Also when creating videos of moving subjects with bodies with Dual Pixel AF (the Canon 70D) there is a advantage to STM lenses compared to the USM counterparts as seen is this video.

A note, the first video seem to come from a commercial channel that aim to advertise Canon and their products. I wouldn't go there if I search for information about the performance of Canon cameras since they just want to sell.

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Thanks Hugo, this looks like the answer I was searching for. Will look for a Dual Pixel AF body. –  plang Jun 12 at 9:12

Perform better than what? at what? The answer to your question depends on what type of shooting you're talking about, and whether or not you're talking about speed or smoothness of AF lock.

STM improves AF performance smoothness, reduces hunting, and is silent for video and liveview shooting with contrast detection--for a body that performs contrast-detection AF with the main sensor. AF performance is enhanced with STM when the main image sensor performs "Hybrid AF"; that is contrast and phase detection AF sensing with the main image sensor. So, IMO, the best body Canon currently has to take advantage of STM is probably the 70D. The 7D does not have a hybrid sensor in it and its main image sensor can only do contrast detection. It is, after all, a 2009 model, and the Hybrid AF only came in with the 650D in 2012.

However. STM is still slower than USM and phase detection autofocus (which uses a separate sensor array; not the image sensor) for stills photography. So, if "better" in your book is faster autofocus lock for, say, fast-action shooting of sports stills, then no, STM is not "better" on any camera body. I shoot an EF 40/2.8 STM on a 5DMkII and 50D. It's slower than my USM lenses to lock focus for stills shooting.

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I'm not sure if the EF 40/2.8 STM is best lens to compare STM v.s. USM, because of the mechanical construction. My EF-S 18-135mm for example is much faster than my EF 40mm in terms of focus spead. Generally a difficult discussion ... USM has also different generations. –  Micha Jun 12 at 6:03

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