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I was given a 450d with a canon 17-85mm lens, it has USM and image stabilzing. It has always seemed okay to me but after a few years i have decided to upgrade to the 700d, which has now come with a 18-55mm kit lens. This one has STM and also image stabilzation.

I am mostly interested in the wide angle of the lens, so the extra 85-55 doesnt do much for me, and the 18-17 is pretty close for me purposes. What I have noticed though, is that the STM seems to be much more quiet than the USM. Is this STM the upgrade from USM or are they different things?

My question is which one has better image quality on the wide end. I am curious as to why as well, besides for seeing that the 18-55 has a wider aperature, the 17-85 just feels better. The feeling i mean in terms of industrial build quality, it seems to be less fragile. I also see that the end of the lens is over 60mm, not like the 52mm of the kit lens or the other intro lenses such as 55-250mm. Does this size have something to do with it?

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3 Answers 3

STM and USM are different kinds of focusing motors. Prior to STM, USM was the preferred option because it was fast and quiet (relative to other kinds of motors that are available). However, it isn't fluid which becomes an issue with video. Enter STM which is also quiet (though I'm not sure which is more quiet) and provides a smooth transition as it focuses rather than a jerky back and forth. My understanding is that USM is still preferred for stills, but STM is preferred for video.

As far as image quality, if you have both lenses available and you can't tell the difference between two pictures that you take, does it matter? I'd recommend looking at sites that review these kinds of things, but Roger Cicala and Lensrentals.com recently compared a couple of lenses and noted that when doing the tests at the wide angle it has to be done near minimum focus distance which is not the typical use case for that focal length. So try for yourself and use which you feel more comfortable with.

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well i just got the lens, and i couldnt find anyone comparing these two lenses. I could do some studies, but If someone here was more knowledgable on the difference, because they are visibly physically different, I would appreciate the advice so i dont chose an obviously wrong one, or find out after awhile that in specific situations one is better than the other but i never did that test. If i should keep both I will, but if one is overall superior than why keep both –  user1938107 Mar 11 at 14:03
    
You can hear the difference between some STM and USM lenses focusing here (as recorded by in-camera mic). USM generates a lot of start/stop focusing noise as it reaches the focus position, while STM does not, as it reduces the 'jolt' as it starts/stops focussing (probably at the cost of a little AF speed). Not all USM are equal though, some will be much faster/slower than currently available STM. Even the fairly new 85mm f/1.2L II has a rather slow USM. –  drfrogsplat Mar 12 at 2:16

According to the Photozone.de, 17-85mm USM is often considered as an upgrade path from the basic EF-S 18-55mm f/3.5-5.6 (not STM) kit lens.

Here is reviews of both lenses:

I don't have either of them, you can compare their specifications on DPReview.com, the 17-85 is wider and has more reach, it also has metal mount, overall it has better build quality, but the new 18-55 STM is lighter and has a new less noisy focus motor which makes ideal for movies, it is also brighter as you mentioned and has better image stabilization.

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The current 18-55 IS is a very sharp lens. Optically superior to the 17-85 over the common range. The build quality is not as good, as well as the AF speed and accuracy.

So the 17-85 is an upgrade over the 18-55, but not a big a one. A better choice is the 15-85.

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if the 18-55 is optically better than 17-85, is the 'upgrade' you speak of just for the focusing and durability? –  user1938107 Mar 12 at 0:28
    
yes and range. It's nice to get out of the "normal" range and get more into the portrait range as well. –  R Hall Mar 12 at 0:43

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