>I think we're talking about two different aspects of the same >topic! The original post was why use ISO 100. And a primary >reason to do so is to allow as wide an aperture as possible at >the 1/250 sync speed
Jon, I'm right with you up to this point.
> to extend the useful range of your flash >for fill.
That's where we part company. I continue to insist that for fill, the range of your flash depends on the intensity of the main light, the distance form flash to subject, and the amount of fill you want -- and it has nothing to do with camera settings. Sorry.