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06-06-2010, 06:29 PM   #1
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Got my ring today

Hi all,

Got my flanged adaptor M42 to K mount today, but now I have a question.

On my *ist-DL, my SMC Pentax-M 1:3.5 135mm K mount gives me focus confirmation, but my Helios-44M(using the adaptor) doesn't.

What's different about a manual K mount lens, and an m42 lens with a K mount adaptor, that tells the camera to let me know when it's in focus ?

Is it possible to mod the lens or adaptor ?


06-06-2010, 07:11 PM   #2
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I started to answer: Is the adapter ring painted black? If so, you need to scrape off the paint on the portion over the mount contacts. I use the file attachment on my Leatherman tool.

But then I tested that with a 50/2 wide open on a painted adapter -- and I got focus confirmation (FC). So I stopped down to f/11 and... no FC. Light is required. I've noticed this with Catch-In-Focus I use with many manual lenses, that there's a CIF/FC cutoff around f/9.5. Many lenses (especially longer) don't get CF above f/8. Wider lenses may get CF at f/11, but never above. How far did you stop-down the Helios? Mine gets FC at f/8 but not f/11, no problem.

NOTE: To use CIF, you *will* need to scrape off the paint. The goal is to short-out those contacts, which is perfectly safe. I often use non-flanged adapters with manual lenses, and on those lenses with wide enough bases, I stick a bit of thin gummed metal tape on the base (before adding the adapter) to short the contacts. DO NOT USE SUCH TAPE WITH A FLANGED ADAPTER! IT WILL JAM ON THE MOUNT!

I hope this helps.
06-06-2010, 07:40 PM   #3
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Thanks for your reply.

Ah ! Is that what it is.

It is a black one. I don't know if it's painted or anodized.

I might chuck it in the lathe and skim the face off it.

I did try the lens at a heap of different aperatures, and took a few photos of items around the house. All the images were a bit dark. Shutter speeds were way too high. Must be the contacts are causing that too. What do you think ?


Last edited by chromo; 06-06-2010 at 07:47 PM.
06-06-2010, 09:33 PM   #4
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Removed coating.
Now perfect. Focus confirmation and shutter speeds have returned to normal.

Your help much appreciated.

Pic (taken with a Panasonic) shows my *ist with Helios lens and new found (perfect fit) lens cap from a Masterfoods jar.

Pretty isn't it ?


Last edited by chromo; 11-21-2011 at 04:22 AM.

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