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06-07-2010, 10:29 AM   #1
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K-7 won't stop down with auto extnsion tube fitted.

K-7 won't stop down with auto extnsion tube fitted...I swear it used to though..

If in mount a lens like the 50mm M series, in manual mode, press the green button or flick the dof preview lever the lens stops down to whatever the value set with the aperture ring is.
If it take it off and fit an auto extension tube (the one with just the lever, no contacts) and refit the lens it now won't stop down when green button or dof preview is operated.
It shoots, but the aperture stays wide open.
this is irrespective of whatever the aperture ring is set to.
in the custom menu I do have 'use aperture ring set' to 'permitted'.
Same result whatever lenses are mounted.

I swear it used to stop down the last time I used the tubes..

Any advice?
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06-07-2010, 10:36 AM   #2
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Without mounting the tubes + lens on the camera, can you check if there is a connection between the lever in the tubes and the lever in the lens? Does the lens stop down when you pull down on it? Was the aperture possibly set to the largest setting on accident?
06-07-2010, 10:59 AM   #3
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Another thing is to check to make sure you didn't accidentally move your mode dial (or forgot you did). Lots of times when moving from AF lenses I forget I am in AV mode and my lens wont stop down when shooting.
06-07-2010, 12:40 PM   #4
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you should check the order of installation on the tubes, some tubes are not necessairly spring loaded and can fail to engage correctly the aperture activation lever because of this. You should as a result mount the tubes on the lens first.

06-07-2010, 12:54 PM   #5
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thanks for replies.

I double checked.. I may have been mistaken about it working on the K7.
I mounted the same lens (135 m series) with a tube on my K10d. Works fine.
Same setup on the K7 - does not stop down.
All other lenses, A-series, M-series, 3rd party all work fine in all modes on the K7. (without tube)


If you mount the tube to the lens and move the actuator it stops the lens down.

I've tried all modes, M is the one I want (and the mode that works on the 10D).

I've tried mounting tube to body then lens to tube, and vice versa.

Looks like i'm not alone..
http://forums.dpreview.com/forums/read.asp?forum=1036&message=35503089

Can anyone actually confirm that they are successfully using an M-series lens with auto-extension tube on a K7.?
06-07-2010, 01:13 PM   #6
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you have peaked my interest, My K7 does the same thing

I have a hunch, and only that.

My extension tubes are black painted mounts, not conducting to short out the pins.

Perhaps we shoud post a question to pentax about this,.

Edit note:Problem confirmed, scratched the paint off the bottom mount of my vivitar auto extension tubes and the lens stops down not

Last edited by Lowell Goudge; 06-07-2010 at 01:33 PM.
06-07-2010, 02:41 PM   #7
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interesting. I'll be trying that tomorrow...
no... sod it...
I'm off down to the kitchen to try..

Incidentally I have written to pentax...

Last edited by katanaismybike; 06-07-2010 at 02:51 PM.
06-07-2010, 02:52 PM   #8
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Yep... that did it.
scraped the black paint of the tube flange mounting face...
TaDaaahhh.. It works.

Lowell.. I owe you a pint..!

06-07-2010, 03:09 PM   #9
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interesting that the 10d worked, but not the K7.!?

Haven't had time to look closely at both camera throats to see what the difference is...
06-07-2010, 03:14 PM   #10
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Nothing to do with the camera other than software, it does not understand all contacts open circuit except that most M42 lenses are non conducting mounts, and perhaps they have elected to not move the aperture pin if there is an M42 mounted. Why bother after all?
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