Manual Focusing when Autofocusing


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theNoobiestNoob

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Dec 14, 2005
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Will damage be done to a lens (say a Sigma 75-300mm f/4.5-5.6 or EFS 18-55mm) that changes its length when focusing if I were to turn the focus ring while the lens is in the middle of a autofocus operation? Is there a difference whether the lens has FTM feature(any damage if manually focusing while lens is still autofocusing?
 

righton

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Aug 28, 2005
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not for Canon lenses........they have a AF/MF select switch..... when its switched at AF, the MF is disengaged from the manual focus ring so u will not interfere with/against the AF mechanism's focusing preferences
 

Watcher

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For Nikon's AF-S, there is true FTM, where even after the AF has locked focus, the user can just turn the focus ring to refocus without the need to touch any switch. This does not damage the lens at all. But only AF-S. The older AF-D needs you to disengage the focusing.
 

Zerstorer

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Jul 8, 2002
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Watcher said:
For Nikon's AF-S, there is true FTM, where even after the AF has locked focus, the user can just turn the focus ring to refocus without the need to touch any switch.
Actually true FTM refers to the ability to adjust AF at any point in time, even during focusing and this is allowed by most AFS lenses.

Others like Sigma HSM allows adjustment only after AF is locked.
 

user111

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Jul 27, 2004
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Canon Ring-type USM allows for FTM :thumbsup:
 

Zerstorer

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user111 said:
Canon Ring-type USM allows for FTM :thumbsup:
Not sure about canon, but does it allow manual focus override even in the midst of AF acquisition?(i.e before AF is locked)

So far, only nikon AFS(except for the 18-55/55-200) and Minolta SSM lenses offer this feature. Sigma HSM requires AF to be locked before the focus ring takes effect.
 

user111

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you can turn the focussing ring anytime without side effects

that itself will qualify for the right to the term "FTM"
 

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