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11-19-2013, 02:00 PM   #1
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Petri 200mm f/3.5, please help

Hi,

I received the above lens yesterday. It has PK mount with no electrical contacts (fully manual). The glass is very clean, the aperture ring moves freely, the blades open and close smoothly when I move the aperture lever with my finger. In short, it is in almost mint condition and I really want to keep it,. However, when I tested it on my K5 and K7, I noticed that it remains wide open regardless of the aperture setting. Thus, all photos were over-exposed. The mount is identical to that on my Pentax lenses. When I activated the depth of field feature on the my cameras, the lens would not respond or dim as I changed the aperture setting. Has anybody had the same experience with Petri lenses? Is there a DIY way to fix the problem? Your help will be greatly appreciated. Thanks in advance and best regards.

11-19-2013, 02:04 PM   #2
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Use it in M mode with green button - it will stop it down - then you can take the shot.
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11-19-2013, 02:13 PM   #3
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Yes, K-mount lenses with no contacts must be used in Manual mode on digital bodies.
11-19-2013, 02:16 PM   #4
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Based on your lens list I'm assuming you're already using it properly, but it isn't acting like your other M lenses as it should. My guess is there is paint on the mount and it is not shorting the body contacts, so the camera assumes it is an M42 or other adapted lens that does not have an aperture lever. Sand this paint off where it touches the contacts of the camera and it should work just like your other M lenses.

11-19-2013, 02:18 PM   #5
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QuoteOriginally posted by manntax Quote
Use it in M mode with green button - it will stop it down - then you can take the shot.
--manntax
Yes, I use it in M mode and with the green button, but it won't stop down. I also tried using with the camera in M mode in conjunction with handheld meter (like I do with my M50mm f/1.4) but the shutter speed keeps changing as if the lens camera was on AV mode. This is very strange.
11-19-2013, 02:21 PM   #6
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QuoteOriginally posted by elliott Quote
Based on your lens list I'm assuming you're already using it properly, but it isn't acting like your other M lenses as it should. My guess is there is paint on the mount and it is not shorting the body contacts, so the camera assumes it is an M42 or other adapted lens that does not have an aperture lever. Sand this paint off where it touches the contacts of the camera and it should work just like your other M lenses.
Hi, I don't see any electrical contacts on the lens mount, but will give sanding it a try. Thanks.
11-19-2013, 02:27 PM   #7
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QuoteOriginally posted by el baroda Quote
Hi, I don't see any electrical contacts on the lens mount, but will give sanding it a try. Thanks.
It just has to be bare metal like the mount of the M lenses so it shorts the body contacts. If there is paint, that is definitely your problem.
11-19-2013, 02:43 PM   #8
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QuoteOriginally posted by elliott Quote
It just has to be bare metal like the mount of the M lenses so it shorts the body contacts. If there is paint, that is definitely your problem.
Thank you very much.

11-19-2013, 02:47 PM   #9
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QuoteOriginally posted by elliott Quote
It just has to be bare metal like the mount of the M lenses so it shorts the body contacts. If there is paint, that is definitely your problem.
Indeed, I have never had a Petri lens in my hands, but I just googled it and found this picture in an e-Bay ad:



So that's most certainly the problem and the solution could be this, which I have done on a similar cosina lens:

11-19-2013, 03:00 PM   #10
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I guess we have identified the problem. Here's photo of the lens mount as it appeared on e b a y. It is painted.
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11-19-2013, 04:26 PM   #11
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I don't know exactly where in the production of cameras this change took place, but my *istD and K10d work and meter fine with painted or black anodized (aluminum oxide is a very good insulator) mounts on lenses and especially extension tubes and teleconverters. My K7 and K5 don't trip the shutter then there is a detected no lens attached , which is what happens when the pins are not shorted. It was discussed a lot when the k7 came out, but not much lately

I have never known why, as it seems to be a change for no good reason
11-19-2013, 04:37 PM   #12
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QuoteOriginally posted by Lowell Goudge Quote
I don't know exactly where in the production of cameras this change took place, but my *istD and K10d work and meter fine with painted or black anodized (aluminum oxide is a very good insulator) mounts on lenses and especially extension tubes and teleconverters. My K7 and K5 don't trip the shutter then there is a detected no lens attached , which is what happens when the pins are not shorted. It was discussed a lot when the k7 came out, but not much lately

I have never known why, as it seems to be a change for no good reason
This is something I will have to read on. I might borrow my son's *ist DS and see if the painted lens mount will work. Thanks for your input.
11-19-2013, 04:39 PM   #13
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It seems to correspond with the introduction of video. I know next to nothing about video on Pentax cameras though, so I have no idea what the reason for it would be.

The older bodies still determined what the lens was based on this. They put the data in the EXIF, "K, M lens" for shorted contacts or "M42 or no lens" for non-shorted contacts, but they didn't change the behavior based on it.
11-19-2013, 08:58 PM   #14
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QuoteOriginally posted by Lowell Goudge Quote
I don't know exactly where in the production of cameras this change took place, but my *istD and K10d work and meter fine with painted or black anodized
I am with you Lowell. These various reports of painted bases throwing things off is new to me as well. I would appreciate somebody doing a controlled experiment to properly characterize the issue.


Steve
11-19-2013, 09:07 PM   #15
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QuoteOriginally posted by elliott Quote
The older bodies still determined what the lens was based on this. They put the data in the EXIF, "K, M lens" for shorted contacts or "M42 or no lens" for non-shorted contacts
Hmmmm...good point.


Steve
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