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Old Jun 24, 2008, 11:25 AM   #1
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hi
holding focus ring, while auto focusing
if this happens by mistake, is the lens likely to break? whos done it?

Canon 70-300mm IS USM

(i think im all out of questions for now, youll be pleased to hear)
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Old Jun 24, 2008, 2:19 PM   #2
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Not a good habit to get into, I must say...Canon's L lenses can be manual focused even with the switch set on AF...The non L lenses are locked to AF when in AF mode...
I would imagine the little tiny gears and motors are not tough enough to withstand
the resistance if your holding the ring...My guess is you will burn out the motor or strip the gears...
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Old Jun 24, 2008, 3:18 PM   #3
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It depends on the AF modes:
1. In AI servo AF the lens will continuously focus so you can't do anything to the AF ring as it constantly adjusts
2. In single-shot AF the focus ring is released after the camera has locked so one can easily turns the AF USM ring to manually overide the camera - even if the manual swich is left in AF mode (this what they call full-time manual overide...)
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Old Jun 24, 2008, 4:24 PM   #4
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NHL wrote:
Quote:
It depends on the AF modes:
1. In AI servo AF the lens will continuously focus so you can't do anything to the AF ring as it constantly adjusts
2. In single-shot AF the focus ring is released after the camera has locked so one can easily turns the AF USM ring to manually overide the camera - even if the manual swich is left in AF mode (this what they call full-time manual overide...)
That is not the case for this particular lens and the 55-250 as well. They do not have full time manual on them. They use a micro-USM motor, not the preferred ring-USM.
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Old Jun 24, 2008, 5:31 PM   #5
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lol i think canon get many people saying there lens is buggered because of this, really its a basic design flaw, cant be hard or expensive to make slip gearing system
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Old Jun 25, 2008, 6:23 AM   #6
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I have done this with my 55- 250, didnt really see it as a problem, as you only rest the lens on your palm or fingers, I dont tend to grip the lens hard, so it simply rotates and rubs a little, then obviously you realise and remove your hand or readjust. More of a problem is the use of a circular polariser which when focusing will need adjusting once focus is achieved.
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