The Sigma EM 140 DG ring flash is the ideal solution to macro flash photography. It has two flash tubes which can be fired both or individually. Each tube's power output can be adjusted manually, though this flash does work with the latest TTL metering systems. The ring flash is attached to the lens using an adapter ring. The flash ring then clips onto this ring. This enables the ring to be rotated to allow different flash angles and shadow configurations. Increasing and decreasing the output of the flash tubes can be used to create shadows in any direction and of different strengths. The advantage of the dual tube system is that it eliminates the very harsh shadows that can be cast by on-camera flash units.

The flash is not powerful enough for portraits of more than 10 feet or so though it functions the best when used for macro work. The flash has one interesting feature. It can fire a burst at a set frequency during a single exposure. This allows correct exposure of the subject, while keeping the background dark. This is a very good flash unit and the overall image results are very good. The TTL metering works well with the D200 and I've had no issues with it.

Definitely recommended for your macro flash needs.

Cheers