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08-10-2012, 12:27 PM   #1
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Focus trap and green button

I was wondering if anyone can help.

I have a Pentax-M 200mm, and a Cosina Cosinon-W MC 24mm.

I expected that both would act similarly, in terms of focus and aperature. Both seem to lack any kind of electrical connectors, so fully manual (focus and aperature).

However, with the Pentax 200, I can use focus trap (so it won't take the picture unless the shot is in focus), and I can use the green button to set the aperature when in manual mode. But neither of these work with the Cosina.

Does anyone understand why this might be the case.

Thanks

Rob

08-10-2012, 01:00 PM   #2
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should work with both AFAIK, I have 2 russian lenses, 1 german, 2 japanese, and 7 taks in m42 and they all work properly. i have had or have another 8 k mount (mostly m and a couple of k series) that also all work that way

I actually don't like CIF because it ties me to center composition so usually i have it turned off

On m42 you will have to step down meter (there is no lever for the system to use is the cosina m42?)
08-10-2012, 01:12 PM   #3
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QuoteOriginally posted by rob_k20d Quote
I was wondering if anyone can help.

I have a Pentax-M 200mm, and a Cosina Cosinon-W MC 24mm.

I expected that both would act similarly, in terms of focus and aperature. Both seem to lack any kind of electrical connectors, so fully manual (focus and aperature).

However, with the Pentax 200, I can use focus trap (so it won't take the picture unless the shot is in focus), and I can use the green button to set the aperature when in manual mode. But neither of these work with the Cosina.

Does anyone understand why this might be the case.

Thanks

Rob
I can tell you why, because I have the Cosina Cosinon-W MC 35mm f/2.8 (and quite a few SMC Pentax-M lenses and a single SMC Pentax-K).

The difference is that the Cosinon is black anodized on the K-mount and thus, electrically non-conductive while the Pentax-M and -K lenses are blank metallic and conductive.

In order to have green button and CIF functionality with the Cosinon, you will have to sand and scrape the black layer away in the segment that is facing the contacts on your camera body's Kaf-mount. It sticks quite well to the metallic base so, a bit of energy is required.


Difference between Cosinon and Pentax-M/K mount(s)
Click to see larger image.

Last edited by Stone G.; 08-10-2012 at 01:18 PM.
08-10-2012, 01:47 PM   #4
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Hello again,

I just took this picture to show what my Cosina Cosinon looks like after the "surgery" described above:




08-11-2012, 03:23 AM   #5
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Thanks a lot. That's very helpful.
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