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12/12/2005 12:53:33 AM · #1 |
Does the USM on lenses ever "burnout" or "die?" I am just wondering if USM ever gets slower over time/use? I just bought a used 70-200 2.8L usm lens and i just want to know if it was a bad idea
-andrew
By the way it is in great shape, no nicks or scratches, the glass is crystal clear. No complaints, I just want to know if i should be concerned about the USM
Message edited by author 2005-12-12 00:56:29. |
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12/12/2005 12:57:53 AM · #2 |
USM if it were to burn out then the lens would cease to auto focus.
USM is 'ultra sonic motor', canon's fancy and high end focusing system. On most if not all USM equipped lenses you can manually focus without flipping that AF/MF button that all other lenses have.
I would think the focus speed woudl remain the same. as parts wear it might get sloppy, or if your battery was low or it was really cold out it might get slower.
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12/12/2005 12:59:59 AM · #3 |
| This lens is my first L lens and i cant really compare it to any other lenses in my bag. So i dont know if it is "sloppy" |
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12/12/2005 01:04:14 AM · #4 |
Originally posted by toiletboy99999:
This lens is my first L lens and i cant really compare it to any other lenses in my bag. So i dont know if it is "sloppy" |
If it focuses correclty all the time, it is fine. if the focus mechanism is worn, then it will not stop preceisly at a given point of focus, but have some freeplay from wear - so the focus will be off at time, possibly back or front focused or both.
I would suspect that USM lacks gears so that is not an issue, but i could be wrong. I was a mechanic in a former life and things bigger than camera and watches i understand. the intracacies of watches and cameras just amaze me to no end.
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12/12/2005 01:57:53 AM · #5 |
Originally posted by Prof_Fate:
the intracacies of watches and cameras just amaze me to no end. |
Yes, I have always enjoyed taking such things apart to study them. Unfortunatly, like my father's 17 jewel watch that I disasembled when I was 10, I'm not always that good at putting them back together. Over the years I have learned that sometimes it is better to just imagine what the inside of a $1500 lens looks like.
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12/12/2005 02:07:54 AM · #6 |
I have built desktop computers lots of times, no probs. Took a laptop apart once..never again!
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