> "Martijn Stol" <[EMAIL PROTECTED]>
> > I've just tried it with my 300/4 L IS, and a Soligor 2x TC, on my eos 30
> > (elan 7e). Normally, with this TC, the camera reports F8 aperture (as it
> > should), and doesn't even try to autofocus.
> > So I've slipped a small piece of paper into the TC, over the first 3
> > electrical contacts *
> > Now the camera reports F4 again, and tries to autofocus. ...
"Julian Loke" <[EMAIL PROTECTED]>
> Great news. I avoided the Canon Tele-extenders in favour of Tamron TCs
> (uggh) since my f/5.6 lenses will shut off the AF on my Elan 7E. Maybe it
> is time to reconsider...
>
> Do you have to cover all 3 electrical contacts?
> Is it possible that the aperture reporting is on one pin?
> And that the signal to slow down AF is on another?
I've just tried a quick test covering 1 or 2 contacts at a time.
Either the camera still reports F4 and tries to focus at full speed, or it
starts acting funny. It's not that easy, i'm afraid.
I wonder if anyone has ever appointed an extension tube volunteer for surgery,
and hooked it up to a scope or pc for some reverse engineering.
(Apart from third party lens manufacturers, obviously. It's probably not easy.
Even Sigma had to rechip some lenses when Canon launched the eos 3 and the eos
30, didn't they?)
Anyway, i have a damaged Canon 1.4x TC lying around. I'm going to dismantle it
and see what's inside, apart from the glass obviously.
That probably won't tell me much though, as its bound to be a single unmarked
chip.
Even if the innards of the Canon TC don't yield any usable information, I might
be able to transplant the electronics to my Soligor 2x TC. That would mean i'd
have a 2x TC which thinks it's a 1.4x TC. If I combine it with my F4 lens, the
camera will report F5.6, and try to autofocus. The TC electronics will slow
down the autofocus, so it should work much better than just disabling the TC
electronics altogether with the piece of paper.
I wonder, the camera might even change its AF algorithm for different aperture
lenses. In that case, using an algorith meant for F5.6 on a F8 lens should work
better then using the algorithm for F4.
Of course, this won't help you much, since your TC already is 1.4x and your
lens is F5.6.
I'll get started on the surgery this evening and let you know what I find.
Martijn Stol
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