I am a fairly new owner of an EOS-800D. Can I use my Sigma EF-500 DG Super ETTL flash with the EOS-800D? The camera seems to have the same hot-shoe contacts as my old camera (a Powershot G5), which implies that it ought to work, but it doesn't. Do I have to do something to enable the external flash? Thanks - Rowan
I think you will find the software on the flash is not compatible with any Canon DSLR newer than the Canon 500D in auto mode. I may be wrong..... but you can probably use it in manual mode or as a slave.
Sigma did update the software and might update your flash but the update was available for DSLR's around the 550D model and it is unlikely that they would be willing to do so now, unless you paid through the nose for it for your 800D, newer flashes are available so if you have a digital camera the flash works on use it for that.