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04-10-2020, 03:41 PM   #1
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KENKO 12mm Macro Extension Tube - Aperture not actuating on digital cameras?

Hello,
So in the craze of the Coronavirus reality, i decided to try some macro photography.
I have this kenko 12 mm extension tube which mechanically is perfect at first sight but when coupled with the lenses i noticed neither my k-1 nor my k-5 can actuate the aperture to the selected value in the lens. when i tried with the mz-5n though it does actuate.
I noticed the mount of the extension tube is anodized black, while generally it is shiny metallic on the lenses.
I suspect there may be a lack of electric contact on the mount which communicates to the camera that there's a lens in place, therefore the camera doesn't actuate the aperture lever.
Can anyone confirm this, and perhaps suggest some solution to teh problem?
Thank you!

04-10-2020, 04:04 PM - 1 Like   #2
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Is it a tube with electrical contacts? If that is the case then it shouldn't matter unless there is no "data" pin on the contact array. If not you'll have to short out the data pin either by removing some of the coating on the mount in that area or attaching some metal foil.

Make sure use aperture ring is enabled in the settings.
04-10-2020, 04:18 PM   #3
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QuoteOriginally posted by Not a Number Quote
Is it a tube with electrical contacts? If that is the case then it shouldn't matter unless there is no "data" pin on the contact array. If not you'll have to short out the data pin either by removing some of the coating on the mount in that area or attaching some metal foil.

Make sure use aperture ring is enabled in the settings.
The tube is totally manual, not a single contact on the mount.

I just checked a plastic mount lens, the da L 18-50 and it does have a bronze contact plate on the inner side, so i guess i will have to file off the coating in certain places.
04-11-2020, 07:24 AM   #4
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First try putting some metal foil over the pins between the camera and tube and see if that makes a difference.

04-11-2020, 08:04 AM   #5
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QuoteOriginally posted by shyrsio Quote
The tube is totally manual, not a single contact on the mount.

I just checked a plastic mount lens, the da L 18-50 and it does have a bronze contact plate on the inner side, so i guess i will have to file off the coating in certain places.
If the tube doesn't have contacts the camera will not communicate with the lens.

In this situation you will need to use a lens that you can manually set the aperture. I doubt the dal 18-50 has an aperture ring. Without that you will be at the widest aperture, the depth of field is going to be thin.

You will want to use the green button to meter. Search green button or stop down metering for settings and instructions

I would not take a file to the lens

Last edited by Sidney Porter; 04-11-2020 at 08:10 AM.
04-11-2020, 08:54 AM   #6
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Without an aperture ring and contacts on the tube if you shoot in Av mode the camera meters and shoots wide open. In Manual the green button will meter fully closed and the exposure will be fully closed as well. However the data pin on the body should be shorted or the green button may not work at all and the aperture may not close down..
04-11-2020, 12:26 PM   #7
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While reading the evolution of the k mount on the forum home page, i noticed that there is mentionet a ground contact on the lens mount. i think that's it. I have to file the mount on the exact same spots i think.

QuoteOriginally posted by Not a Number Quote
Without an aperture ring and contacts on the tube if you shoot in Av mode the camera meters and shoots wide open. In Manual the green button will meter fully closed and the exposure will be fully closed as well. However the data pin on the body should be shorted or the green button may not work at all and the aperture may not close down..
Oh don't worry, i shoot with manual lenses all the time and I'm more than familiar with that procedure. I just brought up the 18-50 as an example of plastic(non conductive) mount.
04-11-2020, 12:50 PM   #8
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If you want to keep electrical contacts between lens and body, you should search a KA extension tube, like the one below (the middle one):




It is not very easy to find and it is not cheap.


Last edited by tryphon4; 04-12-2020 at 03:08 AM.
04-19-2020, 07:33 AM   #9
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It sems I have found the solution to my problem in the forums:
"....it was previously refusing to stop down as other lenses, due apparently to a paint / coating type they used on the lens mount which in effect stops the electronic pins sensing the lens !
So, I tested it with a very thin (thinnest feeler gauge) piece of metal between lens and mount, over contacts....it worked. That simply meant that the camera needed to sense a metal lens mount not a painted / coated one.

Read more at: Porst 55mm F1.2 Color Reflex MC Auto Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database "

as I suspected it is the coating of the mount that fools the camera into thinking it doesnt have a lens attached.
04-21-2020, 07:01 AM   #10
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What I said back in post #2
04-21-2020, 09:24 AM   #11
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QuoteOriginally posted by Not a Number Quote
What I said back in post #2
Yes, you did, thank you!
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