--- Thomas Bantel <[EMAIL PROTECTED]> wrote:
>
> Devin Shieh wrote:
> >> flash just for the A2? Is A-TTL that much better
> than TTL?
> >
> > A-TTL is useless because it's only available in
> Program mode
>
> This is only true for the 540EZ, the older flashes
> do A-TTL in AV and TV
> as well.
>
Hi Thomas,
It's true the 430/420EZ emit the preflash in Av and
Tv, but I don't believe they actually use it for
a-ttl. This behaviour has been discussed before on
the list.
If you're using Av or Tv modes, then the camera
exposes for ambient lighting always and the flash is
treated as fill flash. The flash exposure does not
change the aperture setting or shutter speed in any
way. The camera uses plain ttl for exposure.
A-ttl is for the camera to try and calculate aperture
and shutter speed (in Program mode). In Av and Tv it
is not doing this - you are. The preflash that occurs
is ignored in those modes.
Regards
Gary
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