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02-28-2009, 01:34 AM   #1
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FA 100mm Macro Focus Ring

I just bought a FA 100mm Macro and love it! However, I am curious as to whether it is normal for the focusing ring to over-travel at both ends?

02-28-2009, 02:09 AM   #2
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On my copy, after hitting a "hard" stop (i.e., you're trying to focus beyond the infinity mark), one can still turn the focusing ring, albeit with more effort. It's kind of unnerving since you're not actually moving lens elements anymore. Doing this can't be any good for the lens.

EDIT: sorry, my DFA exhibits this behavior. I don't have an FA, so ignore what I said. :-(

Last edited by gavinhw; 03-03-2009 at 09:27 AM.
02-28-2009, 02:24 AM   #3
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I was thinking maybe they did that to prevent any damage from turning the ring too hard at the stop...
03-01-2009, 04:18 PM   #4
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My D FA50mm is the same. Interestingly enough, the instruction manual states that when focusing manually, one should not turn the focusing ring all the way to infinity or to the minimum focusing distance. Not certain why.

03-01-2009, 07:00 PM   #5
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QuoteOriginally posted by regor Quote
My D FA50mm is the same. Interestingly enough, the instruction manual states that when focusing manually, one should not turn the focusing ring all the way to infinity or to the minimum focusing distance. Not certain why.
LOL, I read that in there, and it makes zero sense. Just how are we supposed to know where the stops are? Doesn't seem to be a problem with any other lens I've ever used- some sort of translation glitch?
03-01-2009, 08:41 PM   #6
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I agree...

QuoteOriginally posted by shiner Quote
LOL, I read that in there, and it makes zero sense. Just how are we supposed to know where the stops are? Doesn't seem to be a problem with any other lens I've ever used- some sort of translation glitch?
This doesn't make any sense to me either, and I simply ignore that remark altogether. This being said, I am curious what prompted the remark in the manual nevertheless.

R
03-01-2009, 09:36 PM   #7
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QuoteOriginally posted by shiner Quote
I just bought a FA 100mm Macro and love it! However, I am curious as to whether it is normal for the focusing ring to over-travel at both ends?
It doesn't happen with my copy. When the AF reaches either at infinity or the minimum focusing distance, the focus ring does not move beyond the focus stops. Turning the focus ring beyond the focus stop manually (very bad idea) when the AF switch is engaged is a sure way to risk damaging the camera body's in-body AF motor or the lens' AF mechanism.

For the DFA seires of macro lenses, one can turn the focus ring manually in AF mode because it has Quick Shift to disengage the focus cam in the lens. The FA lenses do not have Quick Shift, the newer DFA and DA lenses do.
03-02-2009, 02:24 PM   #8
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QuoteOriginally posted by creampuff Quote
It doesn't happen with my copy. When the AF reaches either at infinity or the minimum focusing distance, the focus ring does not move beyond the focus stops. Turning the focus ring beyond the focus stop manually (very bad idea) when the AF switch is engaged is a sure way to risk damaging the camera body's in-body AF motor or the lens' AF mechanism.

For the DFA seires of macro lenses, one can turn the focus ring manually in AF mode because it has Quick Shift to disengage the focus cam in the lens. The FA lenses do not have Quick Shift, the newer DFA and DA lenses do.
I'm talking about MF mode, or off the camera...

03-02-2009, 05:34 PM   #9
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With my copy, the focus ring does not rotate beyond either end of the focus range (or earlier if the limit switch is in effect).

It is quite a definite stop and it seems that it would require quite some force to rotate beyond these limits.

dave
03-02-2009, 06:11 PM   #10
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Like dave kitson has mentioned, my copy also does not go beyond the infinity mark whether on AF or manual focus. It is not supposed to be able to do so, something I have confirmed with my local Pentax people.
03-02-2009, 09:09 PM   #11
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QuoteOriginally posted by creampuff Quote
Like dave kitson has mentioned, my copy also does not go beyond the infinity mark whether on AF or manual focus. It is not supposed to be able to do so, something I have confirmed with my local Pentax people.
Hmm. Should I send it to Pentax? The actual focus does NOT move past the stops- only the ring itself. It is as if the ring isn't mounted solidly, and will "slip" at the stops.
03-03-2009, 06:53 PM   #12
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QuoteOriginally posted by creampuff Quote
It doesn't happen with my copy. When the AF reaches either at infinity or the minimum focusing distance, the focus ring does not move beyond the focus stops. Turning the focus ring beyond the focus stop manually (very bad idea) when the AF switch is engaged is a sure way to risk damaging the camera body's in-body AF motor or the lens' AF mechanism.

For the DFA seires of macro lenses, one can turn the focus ring manually in AF mode because it has Quick Shift to disengage the focus cam in the lens. The FA lenses do not have Quick Shift, the newer DFA and DA lenses do.
Actually, my lens is the DFA 100- I didn't include all the leters in my OP...
03-04-2009, 12:35 AM   #13
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There is nothing wrong with your DFA100 macro. This is just the Quick Shift Focus System doing as it is supposed to.

The reason the focus ring moves past it's 'end' stops is because of the Quick Shift mechanism. The Quick Shift system employs a clutch system that allows slippage in the focus ring which therefore allows you to fine tune focus the lens even when it is in Auto Focus mode and also allow you to trip the shutter. If there was not slippage, then you would possibly ruin the AF drive motor in the camera because you were trying to fine tune focus one way and the camera trying to focus the other way. The reason you may want to fine tune whilst focusing is that the focus point may not be exactly where you want it, or the lens has slight BF or FF.

The distance scale is *not* meant to move past its 'end' stops, only the focus ring should turn, with slight resisitance, past its 'end' points.

So, to sum up.

1) The distance scale markers are not supposed to go past the end stops.

2) The focus ring should be able to turn past the end stops whether in Auto Focus or Manual Focus mode, whether on the camera or off the camera.

3) When the lens is on the camera and the camera is set to AF, you should be able to turn the focus ring even when your finger is half pressed on the shutter button, ie independantly of the AF system. This allows for fine tuning of the focus and still allows you to trip the shutter.
03-04-2009, 12:50 AM   #14
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Very nice, case closed! Thanks.
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