The only system currently available from a major independent, the Sigma EM-140DG is available for Nikon (i-TTL), Canon E-TTL) and Sigma cameras.......
The Sigma EM-140DG is available for Nikon (i-TTL), Canon E-TTL) and Sigma cameras – more a flat-facing twin flash in a ring flash disguise, the unit has a pair of flash tubes either side of the ring, which provide the flash illumination, and a pair of AF-assist lights at the top and bottom of the ring.
The unit is attached to the controller via a heavy-duty coiled lead. There’s a decent selection of modes, including multi-burst shooting and exposure compensation, as well as manual and TTL operation. It also offers wireless operation for hooking up to compatible flash units. The system is reasonably easy to use and fits a wide range of lenses thanks to the included adaptors.
We tested the Nikon-compatible unit and found coverage OK, though at default images are up to a stop underexposed. With some compensation, better results can be obtained with a reasonably even light, though less flat than a true circular ring flash. For flat copy or work against a close background there’s more fall-off than the other units.
For occasional use or for those looking to get themselves a ring flash-type light, the Sigma is a good option.