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Old Jun 21, 2010, 1:57 PM   #1
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Default Explanation of Canon lenses


I recently purchased the Canon EOS 550D with the kit lens as my first DSLR and am now looking at a zoom lens. I have seen some lens with IS and some with USM. So what is the different between Image Stabilizer and Ultrasonic lens? And what is better?

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Old Jun 21, 2010, 2:00 PM   #2
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IS is to counter camera shake and USM is for fast quite focus good for action shooting. You can have IS lenses with and without USM. And USM with and with out IS
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Old Jun 21, 2010, 2:09 PM   #3
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If you'll be shooting sports/action/wildlife, USM is a good idea for quickly focusing on a moving subject. But for those kinds of shots, you'll need faster shutter speeds, so IS isn't important.

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Old Jun 22, 2010, 12:48 AM   #4
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I like having IS on lenses, as I don't seem to hold the camera as well as I use too.
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Old Jun 23, 2010, 5:13 AM   #5
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Originally Posted by 05mpwright View Post

So what is the different between Image Stabilizer and Ultrasonic lens? And what is better?

Image Stabilization (IS) helps to reduce camera shake, especailly while handholding the camera.

Ultra Sonic Motor (USM) assists in focuing the lens quickly and quitely so there is no whining noise as the lens focuses ... this is a useful feature when you want to shoot shy creatures, so the subject isn't distracted/scared, or when you don't want to draw attention to yourself in a theatre or in quiet places. Also, the Ultra Sonic Motor draws minimal power so the camera batteries last longer.

There are two types of USM's: Micro and Ring type.

Ring USM lenses are the best as they allow you to manually focus the lens without switching out of the auto mode ... I prefer this kind as it gives me more control over what I want to do rather than the camera deciding for me.

Micro USM (mostly found on less expensive models) does not have manual focusing capability while you are in auto mode ... IMHO, this isn't worth the money we pay for it ... some opine that "Micro USM was created for marketing purposes to cash in on the reputation of the Ring USM as most people will read the word USM and buy the lens thinking that it is same as the Ring USM" ... I tend to lean towards this oponion.

I prefer an IS lens with Ring USM ... for me, both are important but if I have to choose only one then it'll be IS all the way.
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Old Jun 24, 2010, 8:04 AM   #6
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USM is a great feature because the lens will focus much faster than the ones without it. IS means "Image Stabilization". It gives you up to 4 stops of extra hand-held ability. If you are buying one of the less expensive zoom lenses that has a variable maximum f-stop, for instance f/3.5-5.6, IS may be a huge advantage. If, however, you get a lens with f/2.8 constant aperture throughout the zoom range, you may not need the IS as much.
Always check what other photographers are impressed with about the lens (and what they are not impressed with). DPReview (as well as Steve's) is a good place to look.
Hope this helps.

Last edited by wrasku; Jun 24, 2010 at 8:09 AM.
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