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05-29-2014, 01:09 PM   #16
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The probable reason for only offering a K-mount extension as a single unit
is the constraint enforced by the mechanical screwmount coupling.

Too many connections, and there'll be too much slop for AF to work reliably.

If the 20/36mm set predates SDM, and doesn't have a screwmount connection,
there'd be no way for it to autofocus on the K-mount.

05-29-2014, 02:50 PM   #17
mee
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What use would autofocus have on a macro extension tube? On a full manual stack, I only have to rock the whole camera back and forth a couple of millimeters to focus... not sure how I'd use the focusing ability of this..
05-29-2014, 03:05 PM   #18
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QuoteOriginally posted by mee Quote
What use would autofocus have on a macro extension tube? On a full manual stack, I only have to rock the whole camera back and forth a couple of millimeters to focus... not sure how I'd use the focusing ability of this.
Depends on the situation.
You might have the setup on a tripod,
you might be copying repeated flat items
that don't all sit the same in the holder, . . .

If you want to "rock,"
you can always switch to MF,
and just use the exposure feature,
e.g. with the new D FA 100 WR.
05-29-2014, 04:09 PM   #19
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QuoteOriginally posted by lytrytyr Quote
The probable reason for only offering a K-mount extension as a single unit
is the constraint enforced by the mechanical screwmount coupling.

Too many connections, and there'll be too much slop for AF to work reliably.

If the 20/36mm set predates SDM, and doesn't have a screwmount connection,
there'd be no way for it to autofocus on the K-mount.
That's may why they don't offer the 12mm tube for Pentax because of problems with the screwdrive, otherwise all the other tube sets include a 12mm tube. However the Sony Alpha mount uses both a body based screwdrive and in lens motors.

You'll notice the 20/36mm tubes pictured are for Canon (look at the contacts):


You'll also notice the instructions for the Canon tubes also say to switch to manual focus even though Canon does not use a body based screwdrive system.

KK-C68 - KOOKA OPTRONICS CO.,LTD
QuoteQuote:
1. Set the focus mode switch on the lens to MF (M).

2. Focus the subject manually by turning the focusing ring and press the shutter button to take the picture. (At this point, you can check the focus using the focus mark in the viewfinder.)

3. Manual adjustment is recommended for accurate focusing.
It's rather futile to speculate what the Kooka tubes for Pentax do or don't do based on photos of tubes meant for Canon. Going by the instructions is also meaningless because they give the same instructions about manual focus for all the systems regardless of whether they have screwdrives or not.

05-29-2014, 05:23 PM   #20
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So which person that is more financial then me at the moment is going to buy them, find out the answers and post them on this thread?
05-29-2014, 06:53 PM   #21
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QuoteOriginally posted by mee Quote
What use would autofocus have on a macro extension tube? On a full manual stack, I only have to rock the whole camera back and forth a couple of millimeters to focus... not sure how I'd use the focusing ability of this..
Extension tubes are not limited to macro work.

They are also used with very long lenses (wildlife, birding, etc.) simply to decrease the minimum focus distance. There are a number of applications besides macro.
05-30-2014, 12:45 AM   #22
pid
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... a german dealer has ordered them and is waiting for delivery. If they are in stock I will take a look on them.
Kooka KK-P25 (25mm) 69,- EUR, Kooka KK-P56 (20+36mm) 149,-EUR
05-30-2014, 01:02 AM   #23
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Sorry for my confusion. I have checket this once more - the problem was that some electrical circuits of K-AF2 bayonets could be damaged. At least this happened in my country and I got this news from the official supplier of these extension tubes.

05-30-2014, 01:21 AM   #24
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in which circumstances will this happen?
05-30-2014, 03:12 AM - 1 Like   #25
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From the horse's mouth:

QuoteQuote:
Thanks for contacting Kooka Optics.

KK-P25, KK-P56 support both SDM and Screwdrive. Attached are pictures for KK-P25, pls kindly check.

Best regards,

---
Amy Zhao
Kooka Optronics (HK) CO., LTD | KOOKA OPTRONICS CO.,LTD
Email: amy -at- kooka-optics.com | Skype: amy.zhao0313
Tel: +86 0755 28435910 ext 825 Mobile: +86 15248927294
Add: A16, Silicon Valley New Material Industrial Park, Dafu Industrial Zone, Guanlan, Longhua District, Shenzhen, China, 518110.
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Canon EOS 5D Mark II  Photo 
05-30-2014, 03:33 AM   #26
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QuoteOriginally posted by pid Quote
in which circumstances will this happen?
I wrote everything I know ... I just want to let all of you know that some older extension tubes suffered with this issue. Maybe the situation is all right now. It is necessary to contact some representatives who should be informed more about this issue.
05-30-2014, 05:44 AM   #27
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QuoteOriginally posted by cport Quote
Sorry for my confusion. I have checket this once more - the problem was that some electrical circuits of K-AF2 bayonets could be damaged. At least this happened in my country and I got this news from the official supplier of these extension tubes.
Is this FotoEXTRA?
If so, they are no longer offering the 20/36mm set.

They do claim to have the new 25mm ring in stock,
so it may be possible to check with them,
and have them clarify specifically which rings caused the problems.
05-30-2014, 07:03 AM   #28
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Financial Risk Assumed...

I ordered a 25mm tube from The English Dealer. I will msg out when tested..

Last edited by GlassJunkie; 06-02-2014 at 10:20 AM.
05-30-2014, 12:52 PM   #29
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QuoteOriginally posted by GlassJunkie Quote
I ordered a 25mm tube from The German Dealer. I will msg out when tested..
You may need to borrow a DA 18-55 for less risky testing!
06-09-2014, 10:24 PM   #30
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It appears the Kooka website has been updated and now shows photos of the actual rings which have both the screw drive and SDM/Zoom contacts.
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