Read that it states that the power level should be as strong as the 580 but test with preproduction unit showed that it was weaker. About the same level as 460II. I cannot find any more test result for the production unit that they are selling now. This is a strobist flash. No TTL. Manual. But strong built. Dedicated buttons for easy adjustments. Can use battery packs! and right, got the ready "beep sound".