With 800 Ws of power, we weren’t surprised to find that the Siros L 800 packs plenty of pop. At maximum power, with our Sekonic L-758Dr light meter one meter (3.3 feet) from the Siros L 800’s bare bulb and set to ISO 100 and 1/100 sec., we would have needed to dial in f/45 for a proper exposure. That matches what Broncolor claims. As we stepped down through the strobe’s 9-stop power range, we found that the measured output remains extremely close to the claimed output. As you decrease the output by one whole number on the strobe’s LED, the output decreases by one whole stop, within one or two tenths of a stop of variance throughout most of the range. Only at the lowest setting did we see a greater discrepancy and even then it was within a half-stop.