The SB-900 or flash is an incredibly important tool to wildlife photographers. There’s a ton on the web already on the SB-900 so at this time, don’t have anything more to add but will for wildlife photographers in the future. The SB-900 has this special accessory, the WG-AS1. The purpose of this is to provide protection in wet conditions. The SB-900 handles white balance in a whole new way (and comes with a filter holder that fits inside the soft light dome!) which includes the camera body settings. It has 3 illumination patterns along with a 200mm zoom capability. It doesn’t have a 5th battery compartment but does have the new SD-9. And there is the much heralded better control buttons, switches and panel info. It is THE flash!