Every time I think I have a formula that works somebody publishes numbers that contradict it. If you find some that contradict this formula, please post.
D^2 vs lux does work for a point source, though.

100000 candles [I] luminous intensity
illuminates a spot with
1 lux, E

How far away is it?

R=sqrt(I/E)

316.227766 =calc’d distance in meters, R
345.8266849 =yards
0.196492435 =miles

> The "law" (as in most laws), seems to be consistently disputable

No, not really. The laws of physics apply to everyone (other laws may only apply to those who get caught). And physicists are pretty sure about that inverse square law. However, with non-negligible aperture (head) diameter it is indeed only an approximation, but fortunately in longer distances a very good one. And since throw is in principle a property relating to long distance, there's no reason to do more complex calculations than the inverse square law.

> No one agrees on the perfect set-up

Oh, I completely agree with myself about the perfect setup :) and with other physicists. The more throw it has, the higher the measuring distance needs to be. See here and here. Except for very small lights, measuring at 1m is just not a good idea.

Me too i like your information of any kind. Now i have a number to shoot for in my setup so that i know where the bar is. As far as i know you have the floody-est and throwing-est ( lol ) defiant lighs out there! Definitely like comparing number its like a measring stick. Dont give up!

Edit - its proves if your calibrated eye is right or wrong. Easy way to figure out what works and doesnt. Also you make a lumens measuring device with it like rdrfronty does

Well, that's what I get for letting the derned cat pace off the measurements. I should have told her in feet, not meters!

I guess I will have to do the Defiant "C" light again and start with 1 meter, 2 meters, 10 meters and 20 meters. I had better measure off the distances myself this time.

Someone hurry up and buy it, so I don't have to do the lux measurements again, LOL.