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Old Aug 17, 2005, 8:20 AM   #1
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Hi,

I am in the process of researching into buying a Canon 20D which I know is a lovely camera because I have one at work. I'm also in the process of changing jobs, great equipment but crap employer!

Anyway, I obviously want the best lens I can afford, but I do not understand all the jargon that comes with the Canon lens?

Does anyone know of a guide to Canon lens with descriptions of what all the jargon is? I have searched the Canon website without success.

Thanks

Grant

P.s. If you also know of any great offers in UK I would love to know!
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Old Aug 17, 2005, 8:50 AM   #2
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USM = Ultrasonic Motor = a very fast and silentautofocus mechanism that allows for manual focus as well

IS = Image Stabilization = the lens contains a machanism that helps reduce or eliminate the effects of camera shake allowing you to slightly lower your shutter speed (or increase your f/x)and still get a sharp image

L on a canon lens denotes it as belonging to the "pro" line. These lenses generally are a faster and have superior optical and build quality.
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Old Aug 17, 2005, 9:09 AM   #3
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Be carefull, there are two types of "USM" lenses... the lenses with the fancy ring motors, and the lenses with just a fast motor and a gear box.

The second type is just a commercial thing... One of theadvantages of the USMRING motors is that there is no gear box...
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Old Aug 17, 2005, 9:10 AM   #4
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Right, for instance the 75-300 USM III uses the cheaper USM type, I believe.
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Old Aug 17, 2005, 9:21 AM   #5
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Has anybody a link to this info: Which USM lens is with a ring motor, and which is with a gear box? Or is there a simple criteria?
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Old Aug 17, 2005, 10:01 AM   #6
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http://consumer.usa.canon.com/app/pd...FLensChart.pdf
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Old Aug 17, 2005, 10:04 AM   #7
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Great chart. You would want the Ring USM, not the micro USM. I never realized there was a Ring USM II, now.
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Old Aug 17, 2005, 10:14 AM   #8
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If you go to your local Canon dealer and either get a full canon SLR product catalog or a lens product catalog there is a chart that tells you what lens has what AF motor.

Although the Micro-USM motors are quieter than non-USM, they are still a little slower and louder than the ring-type USM motorsand most of them don't allow FT-M (full time manual focus). I feel Canon is a little inconsistent with what lens get what motor.

For example, I use the Canon 35 f/2, the 50 f/1.4, and the 85 f/1.8. In my opinion these lens should be consistent in what type of motors they have, because they are all non-L's (although the quality of the 50 and 85 is amazing) and are all around the same price point. The 35 has no USM at all, the 50 has a micro-USM with FT-M (the only lens with a Micro-USM that will do this) and the 85 has a ring-type USM.
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Old Aug 17, 2005, 1:28 PM   #9
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Here's a good article that gives you the difference between RING USM and MICRO USM- anyone interested in buying Canon lenses needs to know what they are getting so they won't be disappointed when their "USM" lens isn't a fast as advertised. Honestly, the only lens fitted with the Micro USM motorworth buying today is the 50/1.4 if you have the need for that focal length.

http://photo.net/equipment/canon/lens-motors
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Old Aug 19, 2005, 2:12 PM   #10
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A fantastic Canon resource:

http://www.the-digital-picture.com/


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