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03-26-2009, 04:26 AM   #1
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Quick question

I have a 50-135 DA* lens, when the lens is set to AF should I be able to turn the focus ring or should it be locked in place?. I thought when I received the lens the focus ring seemed to be locked when in AF, but now it turns smoothly in AF or MF..
Thanks in advance for any help..
Allen

03-26-2009, 05:31 AM   #2
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I dont have DA* 50-135mm but i have Samsung's version of DA 18-55mm (kit) and DA 12-24mm. Both has the quick-shift feature, a.k.a I'm able to turn the ring to fine-tune the focus even when the switch on body is set to Auto-Focus. And CMIIW, all Pentax DA lenses have this quick-shift feature.

But normally your auto-focus will override your manual correction everytime, so to make this feature useful, you have to either set Enable AF to OK button, or set OK button to cancel AF (while still holding the button). This way you can auto focus by pressing OK button and then fine tune by manually turn the ring, or if you choose second option, you can auto focus as usual with half-shutter click and when you want to fine tune the focus you hold OK button and turn the ring (while still holding shutter half-click). You can find this settings on Custom Setting menu. And I think this issue has been discussed here in pentaxforums so you might want to search the original thread for more information.
03-26-2009, 06:51 AM   #3
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It's normal. The 50-135 has "quick shift" as does the 12-24 and I assume the other DA* and 18-55ALII lenses as well. The switch on the DA* lenses (I think they all have it) allows you to completely disengage AF without switching to MF on the camera body.
03-26-2009, 07:06 AM   #4
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QuoteOriginally posted by Venturi Quote
It's normal. The 50-135 has "quick shift" as does the 12-24 and I assume the other DA* and 18-55ALII lenses as well. The switch on the DA* lenses (I think they all have it) allows you to completely disengage AF without switching to MF on the camera body.
I believe the quick shift is albeit different on DA's and DA*.
DA-s have a shaft with a mechanical coupler that is engaged only when the camera is turning it.
DA* have SDM. And is missing the shaft completely (correct me if I'm wrong).
The motor being in the lens itself is engaged only when the lens microprocessor is deciding it should.
And more then this: While is totally not recommended to touch the focusing barrel on Da-s while is turning, (you may destroy the coupler, burn the camera motor or brake the gears), on DA* is not that critical: if the microprocessor "feels" the rotating speed is under the rated value (this being a step-by-step motor), and it will cut the supply, allowing you to focus at your will.

So: to answer the first question: Yes, you should be able to turn the focusing ring in both positions of the switch.


Last edited by octavmandru; 03-30-2009 at 05:02 AM.
03-26-2009, 07:17 AM   #5
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The DA*50-135 has both SDM and the "legacy" screw drive support. I'm 99% sure (I only have the 50-135 so far in the DA* lineup) that the 16-50, 200 & 300 have dual support as well. I've not seen the mythical 60-250 or the new 55mm so I don't know if Pentax carried out their threat of not supporting screw drive going forward.
03-26-2009, 10:44 AM   #6
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So: to answer the first question: Yes, you should be able to turn the focusing ring in both positions of the switch..

Thank you very much, actually thank all of you for your help.. whew, I thought I broke something
03-26-2009, 11:52 AM   #7
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QuoteOriginally posted by sajah Quote
And CMIIW, all Pentax DA lenses have this quick-shift feature.
Not all of them do: the DA 18-250 doesn't, for one.
03-26-2009, 11:56 AM   #8
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QuoteOriginally posted by rpriedhorsky Quote
Not all of them do: the DA 18-250 doesn't, for one.
True--that one's a rebadged Tamron.

The DA-L lenses (on the k-m) also don't have quick shift.

But bottom line: you didn't break anything, but you've just discovered one of the reasons I absolutely love DA lenses (with the above exceptions)!

QuoteOriginally posted by Venturi Quote
The DA*50-135 has both SDM and the "legacy" screw drive support. I'm 99% sure (I only have the 50-135 so far in the DA* lineup) that the 16-50, 200 & 300 have dual support as well. I've not seen the mythical 60-250 or the new 55mm so I don't know if Pentax carried out their threat of not supporting screw drive going forward.
That's true too--the DA*55 and DA 17-70 have no support for screw drive. Don't know about the 60-250, but I hear it can use either SDM or the horn of a Unicorn.

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