Stupid question - using on camera flash + a 580EX on stand?

If i setup my 580ex on a stand with an umbrella would it make any sense at all to use my on camera (20d) flash as a fill (Diffuse the on camera a bit with a notecard or something)? Or is this just a dumb idea? Next step for me is getting a 550 or 430 to use as a slave and get stands for it, but until then is it worth experimenting with this? I'm sure its been covered and I know that on camera flash is the devil of lighting but... might as well ask.:o

Might work, as long as the preflash of the built in flash doesn't set off the 580ex, and the 580 is set to manual. (So: 580ex triggered with a PC sync cable or Skyport or the likes)
You might need to experiment a bit fit FEC on the built in flash to dial it down.

Why not give it a try?

Yes, it is possible to use the built-in flash for fill but it will only be able to work in ETTL mode so you would have to play around with the FEC to get the light from it just right.

How were you going to work and trigger the off-camera 580EX flash? I'm assuming it'll be set to manual mode since you won't be able to use it in ETTL mode. And I'm also assuming that triggering will either be via a PC sync cable or an RF remote.

It makes sense to use a on-camera master as fill and to control a slave flash, but the build in flash of the 20D can only operated in auto ETTL mode, the result of working with off camera 580 is inconsistant at best.

Maybe I should just get this used 550 off craigslist for $200 heh.

A 550EX would be a decent slave to my 580 II right?

NJRFilms wrote in post #5563175
A 550EX would be a decent slave to my 580 II right?

Yes, it would.

The 550EX also makes a very decent master for your 580EX II.