I have 3 Nikon SB800′s and one SB900 which i have had a bit of trouble with, Draining Batterys, Overheating just annoying things that would happen at the worst possible time.
Anyhow, i was told about a website just for the SB900 which is called Nikonsb900.net, well what a great site !
it has reviews, how to update the firmware for the flash, tips and even the manual online.
