The sigma em 140 dg ring flash is designed to work with both af 35mm film and digital slr cameras the ring flash is ideal for photographing subjects in fine detail when the shadowless mode is used and is extremely effective for scientific and medical applications dual flash tubes can fire simultaneously or separately using only one flashtube creates shadow which can give a three dimensional feeling to the subject the flash features a guide number of 14 wiso 100 the modeling flash function