Flashes with FEC camera control are:

The 430 EZ; 540EX; 550EX; 430EX; and the 580EX.

Any I missed?
Thanks,
Mike

For your 20D, strike the 430EZ. It's not compatible. And there's no such thing as a 540EX.
Any Canon "EX" series Speedlite can be controlled by FEC in the camera. Only three have the option to control FEC via the flash unit: 430EX, 550EX, 580EX.

There are a few aftermarket brands that have this capability also.

For more info, check out this page.

Thanks Curtis,
Mike

What is best resoucre (book, online, website) to learn how to use the EX flashs. The manual was some help but Iknow there is a lot more that I could doing with them. I have a 580 and 430.
thanks
mike

Mbrescio wrote in post #2718064
What is best resoucre (book, online, website) to learn how to use the EX flashs. The manual was some help but Iknow there is a lot more that I could doing with them. I have a 580 and 430.
thanks
mike

You may try the sticky posts at the top of this forum for helpful links, or search some posts by Curtis (see his reply above) for lots of info, answers, and more links.

Another source is here:
http://photonotes.org/​articles/eos-flash/

Mbrescio wrote in post #2718064
What is best resource (book, online, website) to learn how to use the EX flashes.

The link provided by mahoney is excellent. We lovingly refer to that article as "The EOS Flash Bible". Print it out, read it and keep it for reference.