20D & flash settings

[Nessus]

I have a 20D with a 580EX as master and a 420 and 2nd 580EX as slaves. Regardless or whether I am using the camera flash, a single 580 or all of the external flashes, the 20D shows a 4.5 aperture (blinking to indicate underexposure) at 1/60th (in a dimly lit room, as if the flash was not being taken into effect. Then I review the picture and settings in CS File Browser, those speed and aperture setting are shown. the photographs have a very shallow DOF because of the wide aperture. I have tried to increase the Exposure Factor on the flash, but then the increased flash overexposes the shot and doesn't appear to change the aperture. Then I tried to increase the ISO from 200 to 800, and was able to get the aperture to 5.6, and to 7.1 by increasing the ISO to 1600. While the DOF was better, there seemed to be enough noise at 1600 the the increase of DOF was not worth it.
I have searched the manual to no avail, and the *flash sign appears in the view when I depress the shutter half way and the * button (although I have the camera set to trigger AF with the * button). Do any of you have any suggestions? With that much flash power I should be able to shoot at f/8 at ten feet. Correct?

Thanks,

Adam

[tim]

The first thing to do is read this (http://photography-on-the.net/forum/showthread.php?t=64504), and the huge EOS flash thing it links to. That should tell you what you need to know.

The camera doesn't know there's a flash on it, it's telling you the metering for the background so you can set your shutter speed to capture that. I have no idea what the "exposure factor" on the flash is - do you mean "flash exposure compensation"? Generally if you put the camera in M mode, select whatever aperture you want (lets call F8 the upper limit for now), 1/200th, ISO 400, the flash will fire at the right strength to correctly expose the photo. The flash need to be in ETTL mode.

Perhaps you could post a sample picture, one that has all the EXIF data in it?

[Nessus]

Tim - - Thanks. I did mean FEC when I mentioned exposure factor on the flash. From what you have said, and after reading a article from the link, my feeling that the camera was ignoring the flash is confirmed. I will try M mode tonight.

Adam