The Sigma EF 610 DG ST Flashgun - Nikon fit flashgun features a powerful guide number of 61 and TTL automatic flash exposure control for easy operation. The auto-zoom function automatically sets the optimum illumination angle in accordance with the lens' focal length in a range from 24mm to 105mm. When the built-in Wide Panel is used, the flash can cover the angle of 17mm. For bounce flash, the flashgun head can be tilted up by 90 degrees, to the left by 180 degrees, or to the right by 90 degrees. It can also be tilted down by 7 degrees allowing ease of use for close-up photography. In addition to automatic mode, the flashgun also features a manual flash mode, making it possible to set the flash power to full or 1/16. When the flashgun is fully charged, a confirmation 'ready' light will be emitted and the flash exposure level can be checked through the camera's viewfinder. Other features incorporated into this flashgun include the Auto Power-Off function to help save battery power.