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03-20-2012, 06:52 PM   #1
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Takumar 135 Bayonet lens won't work

I have a 135 Takumar (Bayonet) lens that I acquired recently. While all my manual M42 lenses work in the manual mode on my K7, this one doesn't cause my DSLR to set the shutter speed, and won't cause the shutter to actuate. Any ideas why?

03-20-2012, 06:57 PM   #2
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You need to set the camera to manual M mode, have the use aperture ring function set to permitted and press the green button to set the shutter speed
03-20-2012, 06:58 PM   #3
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Have you consulted this?:
https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
03-20-2012, 07:22 PM   #4
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That worked. I hadn't set the Aperture Ring function to permitted, but now that I did all works fine. It am quite curious though to why my Takumar 105 mm, and my 55 mm (both m42) worked, while this one didn't.

03-20-2012, 07:23 PM   #5
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Thank you for your quick response. Had I known about this forum I would have joined a long time ago,
03-21-2012, 04:15 AM   #6
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QuoteOriginally posted by ash0ash Quote
That worked. I hadn't set the Aperture Ring function to permitted, but now that I did all works fine. It am quite curious though to why my Takumar 105 mm, and my 55 mm (both m42) worked, while this one didn't.
I have not tried but you may find that since the camera reacts to the light coming through, the M42 lenses may simply work. K lenses do require some control from the camera where M42 do not
03-21-2012, 05:57 AM   #7
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QuoteOriginally posted by Lowell Goudge Quote
I have not tried but you may find that since the camera reacts to the light coming through, the M42 lenses may simply work. K lenses do require some control from the camera where M42 do not
That's right: M42 lenses will not stop down automatically on a K-mount body, but stay wide open if the "A-M" lever on the lens is in the A position. So the camera would meter the lens wide open - which is how it would take pictures.
If the A-M lever is in the M position the lens will stop down as you turn the aperture ring, so it will meter at the stopped-down aperture and will expose correctly.
03-21-2012, 06:07 PM   #8
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Likewise, if you try to shoot a non-A K-mount lens on, say, Av, the camera will meter and set the shutter speed just fine for the set aperture, but fail to stop it down. I've never figured out why -- if the camera can do it for M mode, why not Av? Even if you had to manually stop down to set the initial shutter speed, why can't it actuate the stop-down lever when the shutter fires? Av mode would be a Happy Thing for me and my stable of M and K lenses...

PS: Hope you like the 135 Bayonet. Used within its non-multicoated limits, it really is a little honey of a lens. Heck, I should use mine more!

03-22-2012, 03:30 AM   #9
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QuoteOriginally posted by fewayne Quote
Likewise, if you try to shoot a non-A K-mount lens on, say, Av, the camera will meter and set the shutter speed just fine for the set aperture, but fail to stop it down. I've never figured out why -- if the camera can do it for M mode, why not Av? Even if you had to manually stop down to set the initial shutter speed, why can't it actuate the stop-down lever when the shutter fires? Av mode would be a Happy Thing for me and my stable of M and K...!
the issue with AV mode and manual aperture lenses is that the camera does not know the maximum aperture, and the aperture activation lever motion on K and M lenses is different than KA lenses. This is why they call it the crippled K mount, there is one lever missing, that coupled the aperture ring to the body, to tell the cama how many Fstops to compensate for in the exposure setting. Since Av mode implies automatic, and the camera cannot do the function automatically, the do nothing with the aperture control lever in automatic modes, leaving the lens wide open. But the camera does shoot in Av mode and meter, just wide open
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