Using old lenses with an adapter


Link Posted 05/04/2012 - 17:45
This is not strictly pentax relevant but I hope someone will be able to help me. I recently bought a Helios 44M-4 (M42 mount) for a friend to use on his Canon 7D.

With an adapter it should fit on fine but the only thing I don't understand is how the camera will stop down the aperture when a photo is taken. The lens has a small spring-loaded button on the back which when pressed closes the aperture. Will the camera be able to do that? Or is there a special process for using these older lenses?

I have never had to deal with adapters because all of my old lenses fit happily onto my K mount. Good old pentax!

Any help would be great.


Link Posted 05/04/2012 - 18:04
You're really asking on the wrong forum - there are no doubt Canon forums where someone will instantly know the answer.

Thye stop down pin on M42 lenses is actiavted by a plate on screw mount Pentax cameras. It doesn't work at all on K mount cameras, so they are used in stop down, manual mode. That is, we simply set the aperture we require, having set the lens to M (manual) - in this instance the auto/manual switch is referring to aperture control.

Don't know about the Helios lens as there are quite a few variations covering many years.
Best regards, John


Link Posted 05/04/2012 - 18:10
Hi John,

You are right. It's just that I have come to respect and trust the advice that I have had from the regulars on this forum. You have never steered me wrong!

I'll have a look and see if I can identify a manual setting. Your reply gave me a direction for my google searches though and I found this:

It sounds like maybe you have to stick the pin down permanently to get it to work.

Thanks for your help.
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