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03-06-2013, 03:32 PM   #1
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Trouble with manual aperture and tubes

I got some Vivitar AT-22 tubes without the contacts. I have a Sigma 105 attached. My problem is the K5 seems to be triggering the aperature wide open when i shoot. I set the aperature ring to F8 or F16 but each time it shoots like its on F2.8. I took the lens and tubes off and the ring is opening and closing the aperture fine. Its like i need to remove the little flap that goes into the body so that the body doesnt open the aperture all the way when i press the shutter.

After some more reading it seems the tubes are almost doing what they are supposed to. They are holding the aperature wide open while i focus but not letting the lens stop down to where i have the ring set, its just staying wide open.


Last edited by no694terry; 03-06-2013 at 03:52 PM.
03-06-2013, 03:52 PM   #2
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DON'T MODIFY THE TUBES!

Sorry for shouting!

Is the mount of the extension tube, where it mates with the lens mount of the camera body, chrome (bare metal) or anodized ("painted" black)?

If it is anodized, try this: put a piece of aluminum foil between the Vivitar AT-22 tube and the camera, where the electrical contacts on the lens mount are.

If that fixes the problem, you've just confirmed that the anodized surface (electrically insulating) is the cause of the problem. The contacts on the lens mount of the camera has to be grounded for the camera to actuate the aperture lever of the lens). To fix the problem permanently, you can use sandpaper to scrape off the tube to bare metal.

The photo below shows you where to scrape. The issue with the extension tube (actually a de-glassed TC) in the photo is different from the problem you currently have because it has electrical contacts.

Older Pentax DSLRs (K20D and older) do not have this issue.

03-06-2013, 03:52 PM   #3
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Do you have "aperture ring permitted" set to yes in the custom menu?
03-06-2013, 03:55 PM   #4
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What mode are you shooting in? Manual tubes will only work in M mode. How are you metering? With manual tubes you have to hit the Green button to stop down the lens and get a meter reading. Do you have Using Aperture Ring set to permitted in the Custom menu?

03-06-2013, 03:55 PM   #5
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The AT-22 tubes are black. I had to sand mine to get catch in focus to work, but the aperture worked fine without sanding.
03-06-2013, 03:58 PM   #6
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QuoteOriginally posted by bluestringer Quote
The AT-22 tubes are black. I had to sand mine to get catch in focus to work, but the aperture worked fine without sanding.
What camera body? Pentax changed the behavior of the body some time between the K20D and the K-7.
03-06-2013, 04:05 PM   #7
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I set the menu to allow aperture rings the day i got it. I just double checked and its still set. My set of AT-22's dont have contacts. when i pressed the green button it does what it normally does and gives me a basic setting in "M" mode but i was using a flash so i didnt want the cameras choice of a 2 second shutter. Im searching now on "stop-down" metering to make sure im not missing anything.
03-06-2013, 04:06 PM   #8
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QuoteOriginally posted by SOldBear Quote
What camera body? Pentax changed the behavior of the body some time between the K20D and the K-7.

Worked on both my K10 and my K200. Did the K20 come before or after the K200?

03-06-2013, 04:20 PM   #9
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QuoteOriginally posted by bluestringer Quote
Worked on both my K10 and my K200. Did the K20 come before or after the K200?
I think the K20D came after the K200.

I've never used any of the "low-end" DSLRs, but I guess the change of behavior happened with the K-x.
03-06-2013, 04:23 PM   #10
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QuoteOriginally posted by no694terry Quote
I just double checked and its still set..... Im searching now on "stop-down" metering to make sure im not missing anything.
If you didn't set "Using Aperture Ring" to "permit," the camera wouldn't shoot in the first place. That's why I didn't ask you this question.

Try the "aluminum foil" trick to see if it works.
03-06-2013, 04:38 PM   #11
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It must be what SoldBear is referring to. Try the aluminum foil or go ahead and sand them bright, it doesn't take much effort to sand away the black. You are going to want to do that anyway if you use catch in focus.
03-06-2013, 04:41 PM   #12
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If im using all three tubes, do i have to sand all three?
03-06-2013, 04:42 PM   #13
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QuoteOriginally posted by SOldBear Quote
I think the K20D came after the K200.

I've never used any of the "low-end" DSLRs, but I guess the change of behavior happened with the K-x.

I just checked. Both came out in 2008, but I believe the K20 was after the K200, as it is 14.6mp where the K200 is only 10.6mp.
03-06-2013, 04:44 PM   #14
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Actually, I just thought of a simpler test:

With a lens attached, set the camera to M mode, shutter speed 1/2, aperture F/22. Now remove the lens, hit the shutter release button. Does the aperture actuator of the camera body move?

Do the same thing, but before hitting the shutter release, keep a piece of aluminum foil against the lens mount of the camera body to ground the contacts. Does the aperture actuator move when you hit the shutter release?
03-06-2013, 04:45 PM   #15
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QuoteOriginally posted by no694terry Quote
If im using all three tubes, do i have to sand all three?
Just the one attached to the body. The purpose is to ground the contacts on the body.
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