Purchased a Sigma EF-500 DG ST flash off the sell forums here. Neither the seller or I knew that it was incompatible with the Canon 50D. Of course, I happen to have a 50D. Flash would overexpose and zoom in and out wildly never really setting itself. If you are having this problem don't sweat it. Sigma provides a free upgrade for these particular flashguns, they must have EO-TTL II on the back. This is very important.
Here's the link to the upgrade info:
http://www.sigmaphoto.com …eo-ettl-ii-type-flashguns
Note, this upgrade notice is from 2008, but I just sent mine in 10.6.2011 and got it back upgrade and all 10.13.2011. So I know it's still valid and still free (you have to ship it there of course, but return shipping is free)
Also, send it in to Sigma Corp of America in NY, dont call those other service centers (AZ and GA) they dont know or seem like they dont know what you are talking about. I didnt have a good feeling sending it in to those sites. Dont forget to fill out the customer repair form, print it and send it with the flash. Make a copy of it for yourself as well.
Repair form link below:
http://dealerserviceform.sigmaphoto.com …er.do?action=prepare_form
I did not have to send in a reciept, warranty card, box, case or anything with the flash. The repair form ask where you purchased it, I just put down Amazon (even though I purchased it in the forums). I didn't actually have a serial number either. I had used the numbers on the underside of the flash head thinking that was the serial number; come to find out it is not. However, they DID NOT email me, ask me anything, charge me anything. They just sent it back updated, fixed and ready to go.
Hope this helps anyone with this issue.
Now it works awesome, and I saved quite a bit of money!
