calculations for throw,- Never mind, I got my answer in another thread

I got the answer in another thread. Thanks...

So, someone help me here with the calculations for throw. I see the thread I was using is gone, as well as a member.

Defiant 3D @2meters - 24,900 lux and @10meters - 2,800 lux

Defiant 3C @2meters - 76,900 lux and @10meters - 8,000 lux

EDIT: I believe the meter was on x10, not x100 so the readings may make more sense like this???

Defiant 3D @2meters - 2490 lux and @10meters - 280 lux

Defiant 3C @2meters - 7690 lux and @10meters - 800 lux

How do I convert these numbers. The formula I had is gone.

It’s distance x distance x reading. So your 10m readings are 28K for the 3D, and 80k for the 3C.

Thanks. That’s pretty good for the 3C, at least I think so.

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?


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

Yes, pretty much I see, that:

  • Meters aren't accurate
  • Meters need to be calibrated each time they are used
  • If it doesn't cost $XX,XXX, it will not work correctly
  • No one agrees on the perfect set-up
  • The "law" (as in most laws), seems to be consistently disputable
  • What the average person is measuring, is very much, debatable

I am going back to "Hey it's Damned bright" and leave it at that.

That 3D looks like a super flooder from pics and the numbers!

OL, is it possible that the readings you took at 10 meters are incorrect? Or that you measured the 10 meters (distance) out wrong?

Your 2M throw calcs come out to:
3D: 9,960 (2490 x 4)
3C: 31,840 (7690 x 4)

While your 10M throw calcs come out to:
3D: 28,000 (280 x 100)
3C: 80,000 (800 x 100)

The 2M numbers should be pretty close to the 10M numbers so is it possible that the distances (either 2M or 10M) were not measured out correctly?


Defiant 3D 2meters - 2490 lux and 10meters - 280 lux

Defiant 3C 2meters - 7690 lux and 10meters - 800 lux

Lux@ 1meter = Measured Lux x Square of measuring distance in meters

For 2 meters:

Lux@1 meter = measured lux @2 meters x4

For 10 meters:

Lux@1 meter = measured lux @10 meters x100

Nah forget all that. I like your lux numbers, very helpful!

> 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

and as measured by instruments are not the same.

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.

Well, it took some digging but it looks like the average stride of a cat is 6 to 8 inches :wink: