ETTL Mode

I have a 580ex II and a 5D. When I have it set to AV ad in Ettl mode it almost never exposes right. A lot of the time blown out. It i almost like the camera and flash arent talking very well. Can someone talk me through the setting for the flash and camera?

I feel you. I just got the same flash and on my MKII it seems to underexposed quite a bit

PEBKAC

Read this - all of it. It's linked from the stickies. http://photonotes.org/​articles/eos-flash/

You have to learn how ETTL works, and how to use FEC. The Canon system is mostly automatic, but relies on some input from the user.

Every flash photograph is two exposures in one.

If an image is overexposed, you need to figure out if it's from too much ambient light, or too much flash.

No way we can do that without a sample.

Tim,
Thank you. I am goingto start reading that tomorrow. It looks like it will answer all my questions

Or maybe you forgot to activate the high speed sync of the flash. Becoz in AV mode, in 400D the highest shutter speed is 1/200 if the highspeed sync in the flash is not activated. If you are in a very bright location you need to have very high shutter speed or adjust your aperture to a narrow opening. 'hope this will help.