Hi guys, I'm new to flash photography and I'm just starting to explore it's creative possibilities. I just got 2 Nissin I40 units and I was wondering how to have one flash on camera triggering the other flash (I would like to be able to use it in TTL and manual). Will I need a wireless remote trigger or something? This was taken from their website (http://www.nissindigital.com/i40.html): "Slave Mode i40 has a wireless remote flash system as a slave unit. You can enjoy creative flash photography with multiple lightings from the various directions. There are 3 slave modes provided. Slave Digital (SD): i40 synchronizes to the pre-flash system. The master flash is to be set at TTL mode. Slave Film (SF): i40 synchronizes to the traditional single flash system. The master flash is to be set at manual mode. Wireless TTL i40 synchronizes to the wireless remote flash system. (*3) (*4)"