>Indeed IR LED does stand for Infra Red LED, but it sure puzzles me why
>Canon
>use them in the IS lenses. One would expect (hope) if there is an effect
>on
>IR film that Canon would mention it in their literature.
If I just remember it right the IR LED is used to center the
IS element when IS turns off.
Actually I found two years ago a problem with my 100-400 when
I was test-shooting it with my 50E:
I wanted to see how well the 100-400 behaves if I shoot against
(almost) sun.
The sun was low in the evening and I was pointing the lens
towards sun somewhere at 300-400mm position so that I didn't see
the sun in viewfinder but sun was shining deep in to the lens.
When I activated AE and AF the viewfinder image was jumping
couple times and the aperture value became 00. I'm not sure but
it could even be that as long as the IS power was on the lens
was keeping noise and the image was jumping sideways. I don't
remember if I needed to power off the camera (perhaps not)
before things became normal.
I haven't tried it for a long time but it was easily reproduceable
with sun. I have not tried with my EOS 3.
I have *not* noticed the battery contact problem with my 50E
(which might be part of the problem).
I called the Canon service and I think they told me there is
an IR sensor in the IS mechanism.
So I think it might get wrong signals because of bright light
and thus either upset the CPU in lens or body or take
too much current which lowers the voltage (with 50E at least).
I didn't try to get it fixed because it happened only in that
special case (and service wasn't really interested to check it).
But it might be possible to loose a shot because of that.
Vesa
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