The SB-400 gives photographers the opportunity to enjoy brighter and more natural lighting for images taken using a flash. It is designed to suit entry-level digital SLR users while also suitable for more experienced users. Those who have a camera within the D2 series will also benefit from the convenient portable flash unit. The SB-400 offers a guide number of 30 (ISO 200, m), and effortless bounce flash function and is controlled in i-TTL and the D40"s M (manual) mode. Flash shooting distance range from 2 and up to 66 feet Electronic construction - Automatic Insulated Gate Bipolar Transistor (IGBT) and series circuitry Guide number - (at 18mm zoom-head position, 20 degrees C/68 degrees F) 30m per 98.4 feet Angle of coverage - Light distribution covers an 18mm lens when mounted on a Nikon DX format digital SLR camera (27mm lens when mounted on an F6 35mm SLR) Flash shooting distance range - 2 to 66 feet (Varies depending on the ISO sensitivity, zoom-head position, and lens aperture in use) Flash mode - i-TTL, M (manual with the D40 only) Flash exposure control set on the camera - Slow-sync, red-eye reduction, red-eye reduction in slow sync, rear-curtain sync flash, FV lock flash, manual flash (with Nikon Creative Lighting System digital and 35mm SLR cameras) Bounce capability - Flash head tilts up to 90 degrees with click-stops at 0, 60, 75, 90 degrees Power Source - Two AA batteries (1.5V or lower) Flashes/Recycling time at full output - Alkaline-manganese (1.5V) 140/3.9 sec, Lithium (1.5V) 250/4.2 sec, Oxyride (1.5V) 150/3.1 sec, Ni-MH rechargeable (1.5V, 2600 mAh) 210/2.5 sec Lights up when the SB-400 is recharged and ready to fire. Blinks to indicate insufficient light, insufficient battery power and incompatibility of camera with SB-400 Flash duration - Approximately 1/1300th second at full output Mounting foot lever lock - Provides secure attachment to the camera accessory