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03-02-2011, 08:57 PM   #1
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M42 Auto-Takumar pins are safe, but Ricoh pins are not safe, right?

Ok folks, please kindly clarify my thinking on this:

Somebody handed me a bunch of lenses to test and sell for them and they all appear to be M42 screwmounts with the "auto" position. The lenses include a genuine Pentax Tak 50mm 1.4, a JC Penny 200mm 3.3 (which I have never seen before), and a Vivitar 28mm. They all have the pin to allow the camera to activate the aperture mechanism.

I have used M42s on my K-7 before with adapter, but none of them were ever of the "auto" variety. The auto pin gives me pause because it would protrude into the camera body. I'm just worrying about this for nothing, right?

I read about the Ricoh lenses with the pin that needs to be removed from time to time, but that's on a lens mount meant to mimic the K-mount, obviously not the screw type. Nevertheless, this is the kind of thing that makes me nuts; I'm a worry wart.

Thanks in advance! I look forward to testing the 200mm lens, as it's rather unusual. I can't seem to find a review on this anywhere. There are other JC Penny lenses out there, and plenty that match the focal length, of course. But none actually look like this one and it doesn't appear to match a Vivitar/Tokina/etc. design. It's also modestly fast and remarkably light for a lens of this spec.

03-02-2011, 09:16 PM   #2
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I don't think the m42 pin is big enough to get stuck anywhere.

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03-02-2011, 10:21 PM   #3
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You have a lot of leeway because the mount was designed for film. With APS-C, the mirror is much smaller. Also, the K-mount is wider than the screw mount, so Pentax could use M42 adapters and build the K50/1.2 with its huge rear element.

The pin on a Takumar 50/1.4 is just about level with the rear element when focused to infinity.
03-03-2011, 05:13 AM   #4
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K-mount style lenses for Ricoh made cameras (Sears brand is an example) may have an extra pin that lodges in the screw drive hole on Pentax DSLRs and makes removing the lens from the camera very difficult. Not all Ricoh k-mount lenses have that extra pin but it's certainly a good idea to check before sticking one on your camera. Just line the lens up first to how it would be aligned on your Pentax and see if there's a pin that could drop into the screw drive hole. The pin is not hard to remove and Ricoh lenses from that time are almost as good as the Pentax varieties and usually a bit cheaper. I had a Sears 80-200 macro lens that was really very good and picked it up for $10

03-03-2011, 05:24 AM   #5
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QuoteOriginally posted by LowVoltage Quote
Ok folks, please kindly clarify my thinking on this:
...I'm just worrying about this for nothing, right?

I read about the Ricoh lenses with the pin that needs to be removed from time to time, but that's on a lens mount meant to mimic the K-mount, obviously not the screw type. Nevertheless, this is the kind of thing that makes me nuts; I'm a worry wart.
Stop worrying. A KR-mount lens, with an A(P) position on the aperture, MAY have the dreaded Ricoh pin, or maybe just a harmless nub. M42 screwmount pins are NOT a hazard.

A note on M42's -- Three sorts exist:

1) No aperture automation -- one aperture ring, or two rings (preset). These are simple to use: Set the aperture and shoot. With a two-ring preset lens: Set the desired aperture, spin the loose ring up to compose, then spin it down to shoot.

2) Aperture automation with a M/A (manual/auto) switch. Set the switch to M and they function just like type (1). Set the switch to A, and you get aperture automation ON FILM BODIES THAT SUPPORT IT, but on dSLRs they stay wide open.

3) Auto-only, no M/A switch. On dSLRs they stay wide open, unless the pin is jammed or glued down, which can reduce the value of the lens. Avoid auto-only M42's unless you're a film-shooter, collector, or lens doctor -- or you like shooting wide open.
03-03-2011, 12:26 PM   #6
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Thanks everybody!

Again, I knew the dreaded Ricoh pin was limited to a species of K-mount-esque lenses.

I simply haven't used any M42s with the auto switch. I have a 300mm Tele-Takumar 6.3 that works fine with stop-down metering (though I'm going to be letting it go soon, it's going to become redundant). It doesn't have the auto-switch, so I'm never dealt with this situation.

03-03-2011, 04:00 PM   #7
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Remember that if the M42 has the A/M switch, you want to slide it so the M is EXPOSED to use it M mode, which is what you have to do to shoot in the camera's M or Av modes.

You don't slide the switch in the DIRECTION of the M!!!
08-13-2011, 06:03 PM   #8
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Coincidentally just playing with an A/M Takumar 55 1:1.8, the kit lens that came with my Spotmatic back in the 70's. #2 in Ron's comments above. Mounted on the K5 with the Pentax P/K adapter there is absolutely no problem mounting or unmounting. The only (minor) problem is that it will occasionally catch in a gap in the adapter but this is easily solved by holding it down with a thin shim - I used a pen knife blade. I suppose I could permanently depress it somehow but if it ain't broke, why fix it.


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