Like most pro cameras, the Canon 1Ds Mark III does not have a built-in flash, but it does have both an external flash hot-shoe as well as an external PC socket for connecting a strobe. The hot-shoe accommodates all Canon EX series speedlites, as well as a variety of third-party flash units. A Flash Exposure Lock button allows users to lock the flash exposure in advance of the shot, and a Flash Exposure Compensation option adjusts the overall flash power from -3 to +3 EV in one-third-step increments (only for Canon EX series speedlites). Automatic flash exposure bracketing is also available. A High Speed Sync option synchronizes the flash with all shutter speeds available on the 1Ds Mark III, from 1/8,000 to 30 seconds. (Note though, that a full-power flash almost invariably lasts longer than 1/8,000 second, so you won't see the full flash power when working with a shutter speed that fast.) When using a Canon EX flash unit, you can also sync up wireless slave units for greater coverage, with no connecting wires, special codes, or anything. Full TTL flash metering is available even with multi-flash wireless setups. (Canon's series of dedicated Speedlites have a remarkable range of capabilities, really deserving of a review of their own, rather than the very brief treatment I'm giving them here. Unfortunately, I really don't have the time or space to go into all their functions, and the details of how they integrate with the 1Ds Mark III.)
Flash Test Results
Like most professional SLRs, the Canon EOS 1Ds Mark III does not have a built-in flash, so this section left blank intentionally.