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Thread: Mamiya 645 glass with the a900 (a query)

  1. #51
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    Re: Mamiya 645 glass with the a900 (a query)

    Quote Originally Posted by conurus View Post
    Mamiya autofocus lenses have electronically controlled aperture diaphragms, whereas the Sony Alpha mount uses a mechanical lever to control the aperture diaphragm. I think there are fundamental differences in the mount which makes using Mamiya AF lenses impossible on a Sony. Of course, for manual focus Mamiya lenses, all you need is some way to mechanically be able to mount the lens on the camera, and stop down the aperture manually.

    Bo-Ming
    conurus
    How about Contax 645 on A900?
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    Re: Mamiya 645 glass with the a900 (a query)

    I contacted David Llado from Leitax, and unfortunately he is after all not going to do what he told me a few months ago he was planning to do, when he was apparently only waiting for a certain type of chip to make a bayonet for Contax AE lenses. This is what he wrote to me a few days ago:

    "I'm planning to make a Contax-Sony bayonet soon, but it will be only for the MM lenses of small diameter, like my Contax-Pentax bayonet that you can find in my site."

    At the moment I see no way of getting Contax AE lenses on an A900.

    Cheers, Bob

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    Re: Mamiya 645 glass with the a900 (a query)

    Contax 645 glass has an electronically controlled aperture (no ring), so no go. Maybe if you talk nicely to Bo-Ming...

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    Re: Mamiya 645 glass with the a900 (a query)

    That is what I was attempting After all, Contax N must be somewhat similar, being similar vintage. There *is* an aperture ring, btw, but of course, no manual stop-down.
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    Re: Mamiya 645 glass with the a900 (a query)

    The aperture ring of a Contax N or a Contax 645 lens is "fly by wire". It works, on the original N1 body, as follows. The camera body asks the aperture ring for its position, and then sends a separate command to the aperture diaphragm to stop it down (when DoF preview is pressed, or when an actual picture is taken). There is absolutely no direct pathway of any kind from the aperture ring to the aperture diaphragm. It is the same technology used in an Airbus A320.

    My dream is to be able to mount any lens on any camera, but unfortunately, reality sets in and there exists no current technology to make a camera which controls the aperture mechanically to control a lens whose aperture is controlled electronically.

    BTW, I know the newer Nikons such as a D700 is able to do both because the camera body needs to control both PC-E Nikkors (electronic aperture) and all other Nikkors (mechanical aperture control lever). However, no existing lens with Sony Alpha mount is equipped with an electronic aperture diaphragm, and the camera body is not expected to know how to control such a non-existent lens.

  6. #56
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    Re: Mamiya 645 glass with the a900 (a query)

    Is there a dumb adapter? Then one could shoot wide open...
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