Jerry Shaw writes:
I have a new Canon 20D and 580 EX flash. I'm looking for information on using
this combination for fill flash.

Anyone done any flash fill, and have any suggested settings for the
Canon 20D?

Howdy Jerry,

The definition of fill flash varies based on lighting condition and
ISO. Really, what we're talking about is playing with the mixture of
flash light to ambient light, and in a fill flash situation, the
desire is to have mostly ambient light, and just a taste of flash to
punch in the shadows.

One way to guarantee a given amount of ambient light with just a taste
of fill flash is to use Tv modes. Pick a shutterspeed that gives you
the level of ambient light that looks right, and let the camera fill
in the rest for proper expsoure. Warning though, your max flash sync
speed can get in the way here on the top end.

Another way is to use P mode and vary the ISO setting. Higher ISOs
should give you more of an available light mix, lower isos will call
in more flash to make the exposure.

Yet another way is to play with exposure compensation. An old trick
to get more available light and less flash is to go +1 stop on the
main exposure compensation, and -1 stop on the flash exposure
compensation.

I'm not sure there's any one setting that'll work best regardless of
the situation. Try P mode on ISO 200 for starters, and tweak from
there.

Best Regards,
--
Todd H.
http://www.toddh.net/