If it is any consolation, Vue would not be able to prove your hypothesis anyway, even if you could convert Vue light power settings to standard units. There are just too many other variables. Variables include: 1) Amount of wood in the fire 2) Is the wood damp 3) How high and wide are the flames 4) How much atmospheric haze and absorption is there between the fire and the observer 5) And most of all, what other lighting is the fire competing with, bright sun, normal daylight, dusk or dawn, moonlight, starlight, all with and without overcast clouds. PS. I work on Night Vision Systems and would love it if my hobby could be used in my engineering work. But alas, I must rely on boring proprietary computer simulation programs and expensive experiments.