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04-23-2012, 02:48 PM   #1

Auto Chinon MC 50mm 1.7 on K-5


I am a new user to K-5 and I bought the two kit lenses 18-55 and 50-200 WR. Happy with it. As a cheap addition to this I am considering getting an Auto-Chinon 50mm 1.7 lens (the K-mount version). I am not affraid for the manual focus and the aperture ring, looking forward to get to know my camara. I have read the instructions on how to operate manual lenses on this (and other) forums and I think I understand them.

However, I have few questions.

From internet pictures I have seen that the lens has an aperture lever in the mount. The same lever controls the aperture on my current lenses, so I suppose it also does this on the Chinon lens. Correct?

From internet fora I have seen an operation where this lever needs to be removed in order to operate it on new camaras. Does this also go for my K-5? what about the renown compatibility of the K-mounts?

If the camara is controling the aperture, what is the function of the aperture ring?

Curious to learn more about the combination of the aperture ring, aperture lever and controls from the camara...


04-23-2012, 03:35 PM   #2
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You do NOT have to remove the aperture lever. The only two things you have to worry about with third party k-mount lenses are the 'Ricoh' pin and the 'Vivitar' aperture guard. The Auto Chinon MC 50mm has neither.

If you remove the lever the lens will act like a M42 lens in manual. The lens will stop down when you turn the aperture ring and the viewfinder will get darker.
04-23-2012, 03:58 PM   #3
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Boris answered your first questions just right. And this Chinon (sometimes badged as Sears) is a nifty and well-thought-of lens. I have the f/2 version and would indeed like an f/1.7 copy, you betcha!

QuoteOriginally posted by John71 Quote
If the camara is controling the aperture, what is the function of the aperture ring?
The camera does NOT control the aperture, except minimally. A-type lenses have the aperture lever, and electrical contacts on the lens base. Those contacts allow the camera to control the aperture. K- and M-type lenses like this Chinon have only the lever. YOU control the aperture. See below.

Curious to learn more about the combination of the aperture ring, aperture lever and controls from the camara...
If the camera is in any Auto mode, it defaults to Av, and the aperture stays wide-open when you shoot. Put the camera in M mode and hit the Green button; this stops-down the lens to your selected aperture for metering and exposures. So the camera controls the aperture ONLY to stop it down. The rest is up to you.

With K- and M- type lenses on my K20D, I'll typically leave the Mode dial at TAv, right next to M, and the lens aperture set to something comfortable. In TAv the camera defaults to Av and I shoot with the lens wide-open. This is pretty sweet with my K50/1.2! If I need a tighter aperture, a quick-flick of the dial puts me in M mode. I hit the Green button to meter, then hit the shutter to expose. That way I don't have to fiddle with the aperture ring when time may be critical.

Those are the basics. Have fun!

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