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09-03-2012, 08:16 AM   #1
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pentax lens contacts - macro tube problem

I bought a Senz macro extension tube (sorry I have not found any English web site describing this tube - a Swedish descriptions is here PHOTAX - N ). The macro extension tube works perfectly with my Pentax K-5 and SMC Pentax DA 50-200mm/4-5.6 ED WR. Exposure measuring, aperture, auto-exposure, focusing, ... everything works.

However, when I try to use the macro extension tube with Pentax K-5 and Sigma 50/1.5 DG HSM it is a total disaster. Nothing works. Aperture information changes randomly and quickly; exposure indication quickly back and forth between max dark and max light; no focus indicator. If I take a photo it ends up all white or all black.

I guess that the problem is that the HSM lens (lens with built in focus motor) has a different connector layout than the lens without focus motor.

Do we have anyone on the forum that can explain the connectors of the Pentax mount?
Would I have the same problem with a Pentax SDM lens (a Pentax brand lens with focus motor in the lens) like the SMC Pentax DA* 300/4 ED (IF) SDM?

For your information; here is a picture of the contacts on the Sigma HSM lens:


Here is a picture of the tube front:


And here is a picture of the tube back:



Does anyone know of a macro extension tube set that works better?

I bought the Senz macro extension tube set new for approx. US$ 200. I am allowed to return it and get my money back. However, there is not much use doing that unless there is a better working macro extension tube set available that I can buy instead.

Thank you in advance for your help.


Last edited by TB-000; 09-03-2012 at 09:58 AM.
09-03-2012, 09:29 AM   #2
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The HSM (or SDM) contacts are the two square ones closest to the glass at about 10 o'clock on your first image. The other contacts look correct for Pentax k-mount, I just compared them to my tele-converter and everything looks fine with the exception of no SDM contacts on the tube. So you will not be able to auto-focus with this combination as there are no HSM contacts but everything else should work. The only difference between an SDM/HSM lens and a screwdrive are those two contacts. The other contacts are identical.

Try wiggling the Sigma a bit on the mount to get the contacts to seat properly, might be a slight difference in alignment causing the contacts to short improperly. You could also try cleaning the contacts but I doubt that is an issue here.

Extension tubes with contacts are hard to find and many have resorted to buying 2x tele-converters and taking out the glass. So, if I were you I would try everything before sending them back as there are not many other choices. Do you have any other lenses to test? If not it might be worth a trip to a camera store to see if they would let you try the tubes with a few other lenses.
09-03-2012, 09:56 AM   #3
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I have tried wiggling the Sigma HSM. That does not change anything.

I have tested the tubes with 3 different Pentax KA and Pentax KAF lenses without SDM. Those combinations work perfectly.

Of my tested lenses it is only the Sigma HSM lens that does not work with the tubes. (And I am afraid that I might have the same problem with Pentax SDM lenses.)
I understand that I will not have auto-focus with HSM, but I would like to have correct exposure also with HSM (or SDM) lenses.
09-03-2012, 10:29 AM   #4
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You can get similarly weird behavior with a DA* lens on certain TCs or tubes. I have a TC with non-functional PZ/SDM contacts and my DA* lens is not really usable on it. However, my DA* lens does work fine with the other TCs I've tried, either with no PZ contacts or with properly connected ones. So I would venture a guess that a DA* lens would work on your TC. But I certainly wouldn't buy one without a good return policy.

One thing you might look into is whether there is any chip upgrade for the Sigma lens that might improve compatibility. I doubt it, but I know that some camera compatibility problems have been solved this way.

You say that focus works with your DA 50-200 on that TC? There's no AF linkage in the photo you show, so this seems impossible. I've never seen a mount like this before, with 7 contacts but no AF linkage.

09-03-2012, 10:47 AM   #5
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I would look through this thread for some of the problems others have had and possible solutions:

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/113756-pk...ion-tubes.html
09-03-2012, 01:23 PM   #6
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Thank you all for being so helpful.

First a little correction of my statement above: With focusing I meant that the focus indicator works, not that the actual auto-focus works.

When used with Sigma HSM lens:


- If using the macro extension tubes as is: light metering does not work, aperture information does not work, focus indicator does not work. What works is that the camera body correctly identifies that it is a 50mm lens.

- If short circuiting the pin farthest away from the red dot on the front of the macro extension tube (most up on the picture above) with a small piece of aluminium foil: light meter works, focus indicator works, aperture setting works. But, the lens is not recognized as a 50 mm lens (that has to be entered in the menu when connecting the lens). Also the camera shows the max aperture as being 5.6 instead of 1.4. (But photos taken have correct exposure.)

When used with Pentax DA 50-200mm/4-5.6 ED WR:

- If using the macro extension tubes as is everything works: focus indicator, exposure meter, aperture setting, focal length information (but only manual focus, no auto-focus).

- If short circuiting the pin farthest away from the red dot on the front of the macro extension tube (most up on the picture above) with a small piece of aluminium foil: the focal length is not recognized (that has to be entered in the menu when connecting the lens). Exposure meter, aperture setting, focus indicator works.
09-03-2012, 02:12 PM   #7
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QuoteOriginally posted by TB-000 Quote
Thank you all for being so helpful.

First a little correction of my statement above: With focusing I meant that the focus indicator works, not that the actual auto-focus works.

When used with Sigma HSM lens:


- If using the macro extension tubes as is: light metering does not work, aperture information does not work, focus indicator does not work. What works is that the camera body correctly identifies that it is a 50mm lens.

- If short circuiting the pin farthest away from the red dot on the front of the macro extension tube (most up on the picture above) with a small piece of aluminium foil: light meter works, focus indicator works, aperture setting works. But, the lens is not recognized as a 50 mm lens (that has to be entered in the menu when connecting the lens). Also the camera shows the max aperture as being 5.6 instead of 1.4. (But photos taken have correct exposure.)
The pin you short, powers the chip (not the motors) in F/FA/DA/etc series lenses, when not shorted, it is able to send the camera the focal length.
If you short it, the camera 'thinks' an A series lens is mounted, which does not have a chip to inform the camera about its focal length.
Why the sigma behaves this way when the pin is not shorted, is not clear to me.
It would be interesting to see how that sigma behaves on a pre-sdm camera body.
09-03-2012, 02:22 PM   #8
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An explanation of the contacts can be found here

K-Mount Evolution, Features and Operation

See the Ka mount and beyond for the particulars.

If I'm not mistaken, the contact you refer to is the one that carries the digital information from the on-lens chip to the camera. The alignment tolerances for the contacts between the lens and tube are probably just enough on the extremes that it doesn't make good contact. I don't think you want to short this contact to the mount of the tube or lens. Perhaps if you can get a small ball of foil in there that only touches the contact between the lens and tube.

Other than what has been suggested before (cleaning the contacts, jiggling the mount lens) I can't think of anything. Perhaps loosening the screws on the lens mount (both on the lens and tube), jiggling slightly and tightening the screws back up in the hopes that things shift around ever so slightly that they align enough to work?

09-05-2012, 06:14 AM   #9
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I did ask the Pentax and Sigma representatives for more information.

Answer from Sigma representative: The lens is not intended to be uses with extension tubes. If you want to experiment with other brand accessories or your own solutions, that will be at your own risk. It cannot be recommended by Sigma.

Answer from Pentax representative: Unfortunately we cannot comment on why third party extension tubes do not work as intended. Pentax do not sell any extension tubes or teleconverters.

(The answers were not in English, I have translated them.)
09-05-2012, 09:08 AM   #10
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There should be no risk of electronic damage to the camera by short circuiting any of the camera mount pins. That's because the camera is designed to receive all metal mount K and M type lenses which always short circuit the camera pins.

Dave in Iowa
09-07-2012, 10:36 AM   #11
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I have tested the macro extension tubes with "SMC Pentax DA* 300mm F4 ED (IF) SDM". That combination works perfectly, There does not appear to be a general problem with these tubes and SDM/HSM.

I have a theory that the Sigma 50/1.5 DG HSM needs the HSM/SDM contacts to get correct voltage levels for the electronics in the lens. Without the HSM/SDM contacts the voltage levels are incorrect, causing the chip in the lens to send bad and confusing information to the camera body. Do you think that it is a reasonable theory.
09-07-2012, 10:45 AM   #12
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your explanation is quite possible, i suggest trying to use the lens on a body without SDM, if you have one, like an *istD and see how it works.
09-07-2012, 10:55 AM   #13
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Most of the problems discussed in these threads seem to be mostly with Sigma lenses, and not all of them HSM lenses. Myself and several others have had lots of weirdness with tubes with the Sigma 70/2.8 which has the standard drive AF. The problems seem mostly to do with the tube not creating a complete circuit (the tubes usually have one end that is non-conductive except for the contacts themselves, and so scraping off paint or running a wire or foil between ends helps) and in the case of my Sigma blocking off a portion of the mount with tape *between* contacts was also a big help for no apparent reason. (See the thread I linked to above.) Anyway, seems to be Sigma in general rather than HSM/SDM in particular...
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