Canon has eTTL-2. It's got a great reputation. The Canon cameras don't come with built-in wireless control, though. A transmitter (or master flash) on the hot shoe is required. There are quite a few third-party flashes that work with eTTL wireless control.
Nikon has i-TTL. It's got a great reputation. The Nikon cameras don't come with built-in wireless control, though. A transmitter (or master flash) on the hot shoe is required. There are quite a few third-party flashes that work with i-TTL wireless control.
Olympus doesn't seem to have a name for their TTL metering and wireless control. It's all built-in to the camera, though, and can be controlled from the camera body. There are only 2 Olympus flash unit models that support wireless control. Don't know about third-party flashes.
Opinions and/or resources about the different flash systems?
