Help with Canon 600 EX-RT
I'm in need of some assistance with my Canon 600 EX. I currently have two of them and one is not exposing properly. The flash is firing in ETTL and Manual however, in ETTL the images are coming out totally black. When in manual, no matter what the power setting (1/128-full power) they are all completely blown out. The other 600 works normally on all settings on the 5D MarkIII. I've already checked custom functions and personal custom functions and I have them set-up exactly the same for both units.
Things I've already tried:
Cleraring all custom functions and starting from scratch
Removing the flash, putting it back on, turning it off, turning it back on (all the normal trouble shooting procedures)
Any help is appreciated. I'm willing to try anything, hoping it is not a malfunction of the flash but it is looking more and more to be the reasoning. I have had the flash for about 3 months and it worked perfectly until yesterday.