I've had the 7D and 580 EX II working together for years with no issues until recently.
When my 580 EX II is mounted on my 7D it will have a very weak flash when set to 0 flash compensation. Seldomly will it produce a properly exposed image. When adjusting to +⅓ flash compensation it fires as it should consistently and has a nice exposed image just slightly brighter which is to be expected.
When I mount the 580 EX II on my 30D it will consistently fire the proper amount. When I set it to a slave and trigger it via the pop up flash on the 7D it also consistently fires as it should. When I mount my 430 ex on my 7D it fires consistently as it should at 0 flash compensation.
So it appears that the combination of the 7D and 580 EX II at 0 flash compensation is where the problem lies. I have also tried fresh batteries and cleaned the hot shoe and speedlite contacts. Any ideas on this one?
Thanks Peter, I did recently make some adjustments to those settings and put them back to the default setting. I took a number of shots and all them turned out well because the flash was firing the appropriate amount.
I'm still wondering why this was an issue prior to that but all is well now. Perhaps those earlier issues were related to dirty contacts or batteries.