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10-16-2009, 09:29 AM   #1
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Issues with 100mm ?

I just bought the Pentax 100mm 2.8 lens. When I turn the focus ring all the way to the left, it doesn't stop. I have the clamp off, and it will slightly catch, but the ring will just keep on spinning when I focus it manutally. . I was wondering if this is normal or not. I don't have any other lenses that do that, but just wanted to see if it's something that is normal or not. Also, I haven't tried it on my k20d yet, but on the ist ds it has a really hard time focusing. Anyone experiencing that? Thanks.

10-16-2009, 09:36 AM   #2
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what version is your 100? and what do you mean by it doesn't stop turning? there should be a point where it should stop at the designated maximum focusing point distance. if it kept turning beyond that, sadly you got a broken focusing mechanism there.
10-16-2009, 10:10 AM   #3
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I'm not sure what you mean by version unless you mean D FA. By spinning, I mean that I could turn it to the left forever. It doesn't ever end. I haven't noticed it being a problem in AF except for that it is extremely slow to focus. Don't know if that's normal for this lens either.
10-16-2009, 11:41 AM   #4
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I think this is normal for the DFA macros (DFA quick shift is a different mechanism from DA quick shift)

another thread

10-16-2009, 11:58 AM   #5
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I had the dfa 50 macro and the focus ring was working the same way.
10-16-2009, 01:56 PM   #6
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Thank you!
10-18-2009, 11:40 AM   #7
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I haven't had any 100 Pentax macro but on my FA*300 the focusing ring works the same. The scale hits the limit(s) but ring can turn and turn forever. DA* work the same I believe (50-135 did for sure). So I wouldn't be concerned...

BR
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10-18-2009, 05:39 PM   #8
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QuoteOriginally posted by mchud Quote
I'm not sure what you mean by version unless you mean D FA. By spinning, I mean that I could turn it to the left forever. It doesn't ever end. I haven't noticed it being a problem in AF except for that it is extremely slow to focus. Don't know if that's normal for this lens either.
This is normal. It is the quick shift focus mechanism that allows you to change focus without turning the AF off. The lens will hit the limit internally, but the focusing ring will go around and around, with a slightly stiffer feel outside the focusing arc.

10-19-2009, 12:59 AM   #9
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QuoteOriginally posted by Canada_Rockies Quote
This is normal. It is the quick shift focus mechanism that allows you to change focus without turning the AF off. The lens will hit the limit internally, but the focusing ring will go around and around, with a slightly stiffer feel outside the focusing arc.
sorry Albert but I don't think this is quick shift feature.
All DA ltds and normal DA lenses feature quick shift but none of those can move the focusing ring after hitting the limit. + this kind of barrel is on older lenses without quick shift too.

BR
Peter
10-19-2009, 10:36 AM   #10
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QuoteOriginally posted by axl Quote
sorry Albert but I don't think this is quick shift feature.
All DA ltds and normal DA lenses feature quick shift but none of those can move the focusing ring after hitting the limit. + this kind of barrel is on older lenses without quick shift too.

BR
Peter
Both my DA* lenses do exactly as described, and are called to have quick shift. Perhaps it is only the SDM lenses with quick shift that act like this. I'm not sure if my DA 12-24 is supposed to have quick shift, and it has a hard stop at each end of the focus travel.
10-19-2009, 02:51 PM   #11
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QuoteOriginally posted by Canada_Rockies Quote
Both my DA* lenses do exactly as described, and are called to have quick shift. Perhaps it is only the SDM lenses with quick shift that act like this. I'm not sure if my DA 12-24 is supposed to have quick shift, and it has a hard stop at each end of the focus travel.
to my understanding quick shift means that you can manualy override the AF at any time without having to flip the switch on the body or lens.
All DA lenses feature this.

BR
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10-19-2009, 05:10 PM   #12
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This is how it works for any lens whose focus ring does not turn in AF mode. Both my FA* lenses and my DA14 do this. However, my kit lens and 21 Limited turn, but that is because their focusing rings are directly connected.

Nikon AFS and Canon USM (ring types) do this too, and it's fairly unique that lenses whose rings turn all the time have AF override.
10-19-2009, 06:41 PM   #13
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QuoteOriginally posted by jslifoaw Quote
This is how it works for any lens whose focus ring does not turn in AF mode. Both my FA* lenses and my DA14 do this. However, my kit lens and 21 Limited turn, but that is because their focusing rings are directly connected.

Nikon AFS and Canon USM (ring types) do this too, and it's fairly unique that lenses whose rings turn all the time have AF override.
that is if his lens is not an FA type lens. otherwise, setting it at AF mode would lock the focusing ring. this could be a bother if you are shooting a lens with a focus limiter. you need to adjust both the lens focus control level and camera AF switch as well.
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