The i-TTL system supports Advanced Wireless Lighting and versatile functions for up to four groups of Speedlights, with 3 remote i-TTL speedlight groups controlled through the master SB-800. i-TTL Balanced Fill-Flash flash control employs Nikon’s new Advanced Data Communication system to introduce an improved method for the monitor pre-flash and wireless operation that marks an evolution in higher precision over Nikon’s acclaimed D-TTL Balanced Fill-Flash control system and forms the core of the new Creative Lighting System.