Gary Fisher wrote:
> I just checked again. Although the AF assist pattern
> from the 550EX covers the 7 AF points of the EOS 30,
> it doesn't work on the top and bottom AF point (ECF or
> manual selection). I thought it did, but testing
> shows otherwise.
>
> I checked the 420EX and it does work with all 7 (to be
> expected I guess).
>
> I don't know why the 550EX doesn't do this, after all
> it has an area AF assist pattern to suit the EOS 3's
> 45 AF points which covers all 7 points for the 30.
> Presumably some sort of backward compatibility problem
> (as a former Nikon owner I know all about this!).
Hi,
I think I've got the answer to this:
The reason the 550EX AF-assist doesn't work for the
upper/ lower AF-points of the EOS 30/33 & 300
(Elan 7E/7 & Rebel 2000), is because they are horizontal
AF-points (sensitive to vertical lines).
The 550EX's AF-assist pattern, outside the center area,
is made up of only horizontal lines, which means it's only
effective for vertical sensors, which all of the EOS 3 & 1V's
AF-points, except the center point are (when not used
with a f/2.8 lens or faster).
So, though the light "covers" these AF-points of the
7-AF-points cameras, it's of no use to them, as these
AF-points cannot focus on the pattern. That's why it's
not used with them.
Regards,
Johan Berglund
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