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07/16/2005 09:41:28 PM · #1 |
What's the difference between a "USM" lens and a normal lens? Thanks people.
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07/16/2005 09:42:29 PM · #2 |
I believe the differences are that they are quieter and that you can manually focus while set in the autofocus mode.
Message edited by author 2005-07-16 21:42:39. |
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07/16/2005 09:45:06 PM · #3 |
are they worth the extra ca-ching?
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07/16/2005 09:46:45 PM · #4 |
Originally posted by neophyte: are they worth the extra ca-ching? |
faster autofocus
quieter autofocus
full time manual focus = ABSOLUTELY WORTH IT! |
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07/16/2005 09:53:38 PM · #5 |
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07/16/2005 09:54:53 PM · #6 |
Originally posted by mk: I believe the differences are that they are quieter and that you can manually focus while set in the autofocus mode. |
Not exactly. USM is quieter and quicker at focusing than non-USM. Some USM lenses allow you to manually adjust the focus evern in AF mode whereas other do not.
28 - 135 IS USM allows this but the 75-300 IS USM does not.
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07/16/2005 09:54:55 PM · #7 |
Originally posted by faidoi: Ultra Sonic Motor |
hmm, guess I should have add that too, huh?:D |
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07/16/2005 09:55:19 PM · #8 |
Originally posted by superdave_909: Originally posted by neophyte: are they worth the extra ca-ching? |
faster autofocus
quieter autofocus
full time manual focus = ABSOLUTELY WORTH IT! |
Can't argue with that formula. Thank you!
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07/16/2005 09:56:33 PM · #9 |
Originally posted by superdave_909:
full time manual focus = ABSOLUTELY WORTH IT! |
This is not on all USM lenses.
Message edited by author 2005-07-16 21:56:52.
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07/16/2005 10:00:10 PM · #10 |
Originally posted by cpanaioti: Originally posted by superdave_909:
full time manual focus = ABSOLUTELY WORTH IT! |
This is not on all USM lenses. |
What?! The Formula is flawed???
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07/16/2005 10:02:07 PM · #11 |
Originally posted by neophyte: Originally posted by cpanaioti: Originally posted by superdave_909:
full time manual focus = ABSOLUTELY WORTH IT! |
This is not on all USM lenses. |
What?! The Formula is flawed??? |
Yup. I have two USM lenses. One has this feature, the other doesn't.
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07/16/2005 10:04:48 PM · #12 |
But The faster and quieter Autofocus has to be worth it or no? I'm contemplating moving up to a DSLR, but I'm taking my time to learn as much as I can so I can make an informed Decision. (I'm leaning towards the EOS20D)
Message edited by author 2005-07-16 22:05:11.
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07/16/2005 10:05:23 PM · #13 |
Originally posted by neophyte: But The faster and quieter Autofocus has to be worth it or no? I'm conteplating moving up to a DSLR, but I'm taking my time to learn as much as I can so I can make an informed Decision. (I'm leaning towards the EOS20D) |
yeah it's worth it.
//www.kenrockwell.com/tech/20dd70.htm
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07/16/2005 10:06:40 PM · #14 |
Originally posted by neophyte: But The faster and quieter Autofocus has to be worth it or no? I'm contemplating moving up to a DSLR, but I'm taking my time to learn as much as I can so I can make an informed Decision. (I'm leaning towards the EOS20D) |
Yes. I was just trying to provide accurate info. The fact that a lens does not have the full time AF should not deter you from getting it. I use the feature rarely so it makes no difference to me.
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07/16/2005 10:11:28 PM · #15 |
There's a chart here (pdf) of Canon lenses that tells which have the feature and which do not. |
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07/16/2005 10:13:46 PM · #16 |
USM = Ultra Sonic Motors which move the lens to focus. The length of the lens does not change during focus.
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07/16/2005 10:19:46 PM · #17 |
Originally posted by Alienyst: USM = Ultra Sonic Motors which move the lens to focus. The length of the lens does not change during focus. |
So all USM lenses are IF? I didn't know that.
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07/16/2005 10:20:48 PM · #18 |
Originally posted by kyebosh: Originally posted by Alienyst: USM = Ultra Sonic Motors which move the lens to focus. The length of the lens does not change during focus. |
So all USM lenses are IF? I didn't know that. |
That's not true. The length of the 75-300 IS USM does change during focusing.
edit: there's also two types micro (inferior) and ring. It could be the one's with ring USM are IF and have full time MF though this info is not mentioned in the chart posted by mk.
Message edited by author 2005-07-16 22:36:56.
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07/18/2005 03:35:07 AM · #19 |
A USM lens uses piezo electric wave vibrations to move focus the lens. The result is quicker, quieter and more accurate focussing with hardly any time to stop and start. The ring type also have an automatic disc-brake effect so the lens is held in focus by the ring. Very useful for shots where the camera is not horizontal.
They do not all have manual focus override.
Not all are fixed length.
The USM motor is only related to the focussing and therefore there are different technologies in play with focus override and lens length change. Not to be confused.
If you have a USM you WILL notice the difference and will not be going back. The speed, noise and accuracy are astounding - especially in the high-end L series lenses which generally use the ring type. |
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07/18/2005 07:53:35 AM · #20 |
Originally posted by cpanaioti: That's not true. The length of the 75-300 IS USM does change during focusing.
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Interesting...I have the Canon 75-300 IS USM lens and it doesn't change length when focusing. Don't know what you have.
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07/18/2005 08:29:56 AM · #21 |
USM is a technology which provides quieter and faster focussing of Canon lenses, it does not directly affect whether the physical length of the lens remains constant during focussing. This is down to the design of the lens and positioning of the elements.
The Manual autofocus feature is not available on all USM lenses but is a very useful feature.
My own criteria for selecting a lens is more influenced by the sharpness of the glass and low f-stop not the speed or quietness of focussing.
Having said that my 16-35 'L' has just about all the most desirable features, ultra-sharp, low f-stop, incredible USM autofocus speed, manual focus over-ride and constant lens length, however the price tag to get that lot is scary, very scary.
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07/18/2005 10:04:06 AM · #22 |
.
edit: not worth arguing about
Message edited by author 2005-07-18 10:13:28.
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