This terminology was originally used in 1985 by Inverse Square Systems in conjunction with their “Stroblox” series of high-efficiency self-contained flash units. The term was created because most manufacturers of flash equipment (as well as the press) insisted on the incorrect use of the term “wattsecond” as a definition of light output (in such wrong statements as “This system puts out 800ws of light”). Since the Stroblox system produced on the order of twice the amount of light per wattsecond as did the average “box-and-cable” system at the time, Inverse Square Systems chose to employ the rating “2400 effective wattseconds” as a means of saying “our system puts out an amount of light equal to the average 2400ws system,â€ even though the actual stored energy of the Stroblox 2400 was only 1200 joules or wattseconds. Indeed, this terminology gave the user a more clear idea of what to expect from the unit than he would have gotten had they simply stated that it was a 1200ws system. We publish wattseconds, effective wattseconds, and Lumenseconds for our flash units, with Lumenseconds being the most valuable method of power comparison.