Professional i-TTL Speedlight compatible with Nikon FX and DX format SLRs, and part of the Nikon Creative Lighting System. This powerful Speedlight offers photographers extensive creative opportunities for their flash photography. Three illumination patterns - Center-weighted, Even and Standard - provide total control over flash coverage and it covers a class-leading auto zoom range of 17-200mm in just 1.2 seconds. Advanced features include a booster circuit that enables high-speed recycling using four AA-type batteries and a built-in thermal protection system to warn of excessive heat build up. The SB-900 can automatically detect the presence of a fluorescent or incandescent color filter and transmit this information to the attached camera's white balance setting, and its firmware can be upgraded via the camera body.