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02-13-2011, 03:06 AM   #1
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K-X Problem with Extension Tubes

I recently bought a set of extension tubes from ebay. This set does not have the electrical contacts, but does have the levers required to operate the aperture. I understand that some functionallity will be lost.

So trying to use said tubes in manual mode on my k-x, I've come across a strange behaviour.

Using my 1.7 50mm from my old ME-Super, I can use the green button to have optical preview, and manually set aperture/speed. I hear, and see, the aperture shut down.

Putting one or more extension tubes on the same configuration, green button no longer works.

However, if I use live view, changing the aperture changes the image (but I can't work out how to meter in this mode).

And, if I take a couple of shots at different apertures, I get different exposures, so the aperture is being closed.

I get the same behaviour with my Sigma 28-135 lens.

Can anyone offer any suggestions on where I'm going wrong, or why the tubes are not fully compatible?

Thanks

Lloyd

02-13-2011, 06:32 AM   #2
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I will guess the tubes and mounts are black

You need to sand the paint off the mount where it touches the body contacts. I discovered this with my K7 also
02-13-2011, 06:41 AM   #3
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That was the only difference I could see between the two. Do you know what the electrical contact is doing?
02-13-2011, 06:49 AM   #4
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Some pentax cameras want a connection to the lens mount on the last pin. Furthest away from the lens locking pin to confirm manual focus

02-13-2011, 09:06 PM   #5
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Lowell, you're amazing!
02-15-2011, 12:16 PM   #6
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Thanks Lowell. Having attacked the mounts with some 180 grade emery, the green button is now stopping the lens down. I think it is the data pin that needs to be grounded, which is around 5 o'clock on the lens.
02-15-2011, 12:56 PM   #7
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QuoteOriginally posted by Lloyd Quote
Thanks Lowell. Having attacked the mounts with some 180 grade emery, the green button is now stopping the lens down. I think it is the data pin that needs to be grounded, which is around 5 o'clock on the lens.
correct, last pin from the lens locking pin.

Bit of a Pain really, the camera should figure out nothing is talking, but I guess it can't
02-15-2011, 02:32 PM   #8
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Won't aluminum tape do the same thing?

8 bucks for a roll that will help modify about a thousand lenses.

07-05-2011, 10:46 AM   #9
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Thanks Lowell just tried with piece of aluminium foil works fine now need aluminium tape or conductive paint as my extinsion tube back plate is plastic.
09-01-2013, 09:11 AM   #10
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I have a similar problem but maybe not quite the same. I am trying to use a Vivitar Auto Extension Tube Set AT-22 with an M 50mm f1.7 mated onto a K-r. I have set the Green Button and the required permissions in the Settings menu and the M lens works perfectly as a manual lens should (nice lens - have had it since 1981). However, using the tube set the Green Button will not operate when I use the viewfinder to compose and shoot in the normal way. However, if I switch to Live View the Green Button does work. I can use LV to set the aperture and then switch to the viewfinder - but this seems cumbersome. The forward facing surface of each of the three tubes in the set is metal but each rear face is black painted - possibly metal or maybe plastic. Changing the order of the tubes doesn't make any difference. The tubes themselves seem sturdy and well-made and are in good condition.

So is this a case of conductivity again - or is it something different? I have searched the forum and this thread seems closest to my problem. I would love some advice - can anyone help?
09-04-2013, 12:32 PM   #11
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QuoteOriginally posted by manstanox Quote
So is this a case of conductivity again
The behaviour you describe is exactly what one would expect if there is no conductivity - for the body it will mean "no lens attached".
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