F. Craig Callahan wrote:
> [...]
> reports f/2.8. The extension tube, in effect, "negates" anything
> mounted between
> it and the camera, in terms of what the body "sees." I thought this was
> interesting.
Yes. When you think about it, this is to be expected. The tube doesn't
have the 2 extra contacts
(like the TCs) that are needed to transfer the information about
aperture changes.
Because only lenses meant to be used with the Canon TCs have these
contacts at the rear end,
while TCs and tubes don't have them, it is not possible to get correct
aperture readout
with more than one TC. It wouldn't work even if you could stack the TCs
directly without a tube.
Thomas Bantel
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