> Hello,
> I have an A2E and I just bought a 100-300mm f5.6L lens with a Tamron
> 1.4x SF AF tele-converter. With the tele-converter on, the AF seems
> quite confused. Sometimes it finds the correct focus and other times,
> the noisy non-USM lens just goes back and forth from minimum to
> maximum focus.
> Also, the largest aperture without the converter is 5.6. When I put
> the converter on the largest aperture is still 5.6 not 8.0.
> Does anyone one have advice or experience with these issues? I plan
> to go to Kenya in late December/January and I hope to get some good
> photos.
> Charles
The Tamron tele-converter is not reporting the correct aperture to the
camera body. You will be shooting at f8, even though the camera says f5.6.
There is a reason A2E's are supposed to stop AF at 5.6 - at a slower
aperture, AF becomes slow and confused. Rather than let the camera make
mistakes, Canon just disables AF. In bright light/high contrast subjects,
this may not be too much of a problem. You can always manual focus.
The camera should still meter correctly, although you may have to use
aperture priority (or full manual) and set it to > f8 for correct exposure
(if you leave it at 5.6, the camera will under-expose by a stop). (somebody
may want to confirm the last bit for me, Im just guessing)
While in Kenya, you may want to take some film faster than 100, unless you
use a tripod. At ISO100, f8 in bright sunlight you will be getting 1/200
(maybe up to 1/500 in *really* bright sunlight). 1/200 isn't really enough
to stop shake at the long end. ISO400 speed will give you around 1/1000
which will be fine - although if it becomes overcast, you may be in trouble.
- Stuart.
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