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12-04-2011, 03:57 PM   #1
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Vivitar 135mm 2.8 with on K5 with no DOF or Green Button

Hi all,


I have been using Pentax since 1986 when my grandfather bought me a used ME Super and some lenses. One of the lenses is a great manual focus Vivitar 135mm 2.8 K-mount.


On my older K10 the DOF and the Green Button will work fine with the Vivitar 135 stepping down the aperture just fine.


On my new K5 nether the DOF or Green Button will step down the aperture on the 135. I have set “Using Aperture Ring” to “Permitted” and have two other manual K mount lenses that work fine with the DOF and Green Button on the K5.

I really like shooting with the old 135mm lens, but I like steeping it down when needed. Has anyone else had a similar issue with the K5 and older lenses, perhaps I missed a setting? Anyone have any ideas on how to tell if this is an issue with the camera or the lens? Am I just stuck shooting wide open?


Thanks for your time.

12-04-2011, 04:30 PM   #2
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Check the lens on another body, it could have developed a fault.
12-04-2011, 04:33 PM   #3
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Dumb question: does the aperture actually work? i.e. with the lens off the camera and stopped down, you should see the blades be closed and you can open them with the spring-loaded aperture control on the mount (and they instantly close again when releasing). If all is well with the lens, it should work unless it is not mounting correctly. Is it one of those Vivitars with the too-big flange next to the aperture control? (Are you in M mode? You should be in M mode.)
12-04-2011, 05:44 PM   #4
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Dark_Mist, I did check this lens on my K10 and it works fine on that body.

vonBaloney, The blades do close when I manipulate the aperture control directly on the lens. I am in M mode. The too-big flange next to the aperture control sounds like something to check. Do you know how to tell?


Last edited by jstormes; 12-04-2011 at 06:00 PM.
12-04-2011, 06:07 PM   #5
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If the flange was too big, it wouldn't mount properly at all or would be scraping stuff in the mirror box -- it's that guard next to the aperture control -- compare it to a Pentax lens (which looks like a shark fin). Some of the Vivitars have a much bigger one.

You cleaned the contacts, you might try cleaning the metal of the lens itself even though it has no contacts (it needs to short the pins probably) and make sure the lens mount is not deformed in any way. The K10 will attempt to close the aperture with the green button even with no lens, but the K-5 will not so it isn't recognizing that there is a bayonet-mounted lens there for some reason.
12-04-2011, 06:18 PM   #6
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Is the part of the lens mount that touches the camera contacts black anodized, or bare metal? If it's painted/anodized you may need to sand it a bit, so that it shorts out the data contact on the camera, the same way you would to use CIF.
12-04-2011, 06:27 PM   #7
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vonBaloney, I think you are on to something with the contacts. I just tried what you eluded to with both my K5 and K10. The K10 will indeed attempt to close the aperture with no lens attached, while the K5 will not. The two manual lenses I have that work both have shiny silver mounts, while the lens that will not work, has a black mount. A quick check with Ohm meter shows the working lenses conduct quite nicely, while the non working lens is a poor conductor.

Awesome observation, not sure if the issues can be fixed but I can quit pulling my hair out.
12-04-2011, 06:49 PM   #8
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QuoteOriginally posted by jstormes Quote
not sure if the issues can be fixed
This has been noted before on the forums - a few lenses have this issue and they are the K mount lenses that have the painted flanges or plastic flanges; you can simply short the contacts with a piece of aluminum foil and you should be fine...

12-04-2011, 06:57 PM   #9
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QuoteOriginally posted by jstormes Quote
not sure if the issues can be fixed but I can quit pulling my hair out.
Wondering if my post above is invisible. Assuming the mount is metal, I suggested the easiest way to deal with it. Foil and metal tape are also options, but better for m42 lenses than K mount. The extra thickness of it can make it difficult to remove the lens later, if it bunches up at all when attaching the lens.
12-04-2011, 07:52 PM   #10
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Ok, mystery solved -- it needs to short the contacts. You can use foil or metal tape as suggested, or as long as you don't mind making the lens a bit ugly just file or sand it down to get to bare metal. You'll want to make it smooth so it is not abrasive when mounting...
12-04-2011, 08:26 PM   #11
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Now that we understand the problem, I find myself looking for conductive tape.

Has anyone tried any brand of conductive tape, and if so what type of success have you had?
12-04-2011, 08:33 PM   #12
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Metal tape used for ductwork is very thin -- would probably work but may rip apart as you turn the mount. Make sure you depress mount release button fully as you mount so it isn't sticking up. Another option is simply to swap the bayonet from some other garbage lens -- find one with matching screw holes or make new holes. If you have a camera store nearby that sells used equipment, they often have a junk pile of $5-$10 lenses that are broken or just really undesirable...
12-05-2011, 11:03 AM   #13
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If the mount is metal and painted just scrape a little off. If it is plastic yoou need tape
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