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 degree