CANON DIGITAL FLASH
The message began like this:"Help! My Canon 540EZ flash doesn't work on my new digital SLR."
That's right. I found that out myself
. Canon "EZ" series flash units that were made for film cameras don't work at all or with very limited functions on the digital SLR bodies. You need one of the "EX" series flash units. Two good current models are the Canon 430EX and the Canon 580EX (see the links below).
A higher model number means a higher guide number (i.e. more light output). At maximum power, the 580EX puts out about one more stop of light than the 430EX. The 580EX has a few more electronic bells and whistles, like the ability to fire other flash units via an infrared remote signal. If you don't need the extra power or the extra bells and whistles, the 430EX will be just fine.
You can also buy discontinued EX models like the 550EX, the predecessor to the 580EX, or the 420EX. Look for used flash units at KEH.com
and other used photo equipment dealers on my LINKS