A different kind of teleconverter.

Started May 7, 2012 | Discussions thread
Veteran MemberPosts: 3,428
Re: Let me try a different explanation.
In reply to brandrx, May 8, 2012

But like I said if you short out the AF pin the camera will not treat the lens as AF no matter what else you do. It will get no feedback from the lens when AF is occuring. So it will not be able to work the screwdrive.

This is similar to what Canon tried to do when they completely overhauled their lenses when they went to AF. I think they considered screw drive as a possible backup to electronic drive but could not figure out in those days how to make both work or either work alone. So they went cold turkey with electronic drive and motor-in-the-lens.

All you really need is a TC that would block (not short) the SDM contacts. Similar to how a 3rd party non-PZ contact TC works on a lens with both SDM and screwdrive as I understand it (I own no SDM lenses at this point).
Kent Gittings

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