I'm new to the Lighting forum, so I'm sure there is a conversation out here that addresses this (if so, please let me know). I'm looking for a quality ring flash to use a Nikon SB-900, or an affordable option from another vendor. I've heard of the RayFlash adapter (which appears to be very popular), but not many other adapters. I've also seen the Nissin MF-18 (which looks very good, but apparently has not been released yet). The Sigma EM-140 also looks good. Anyone have suggestions for something portable?