Nikon SB-21 Macro Speedlight system is designed for close-up flash photography in combination with Micro-Nikkor lenses. The SB-21 is an easy-to-use unit offering TTL flash exposure control. The macro flash unit does not provide auto exposure. Manual calculation is required with its Full or 1/4 power output. The SB-21 has advanced electronics assure consistent exposure control with variable output. This flash unit is designed for F3-series cameras and compatible with all Micro-Nikkor lenses.