InfidelCastro said:
Throw and brightness are two different things.
Ah, great, someone who understands these terms. Hopefully you can straighten me out.
I understand that the total light output, or luminous flux, from a light is measured in lumens. Ok so far. The luminous intensity is in candelas, which can be different for each angle or direction but isn't a function of distance. And the illuminance or illumination at some distance and angle is measured in lux, which is a lumen per square meter. Ok so far, I've got those.
The problem is with "brightness" and "throw". I don't see either of those on the sites talking about light. So I've been using "brightness" to describe, well, how bright a beam is -- that is, if my eyes smart and I have to put my sunglasses on to look at it, I say, wow, that's bright. If I took a flashlight and blurred its focus so that it's putting out the same overall amount of light but in a much broader beam, I'd say that the beam isn't as bright as before. My lux meter tells me that the illumination (lux) is less at the same distance, I can't see as far away, and I can take off my sunglasses.
But I guess that's wrong. Are you saying that it's just as bright as before because the luminous flux (lumens) hasn't changed? Hm. Ok.
Now in Flashlight Reviews, the reviewer calls the square root of the lux at one meter (which is the square root of the luminous intensity or candelas) "throw". That makes sense to me -- it's a distance, the distance at which the light casts an illumination of one lux.
What I measure is the illumination in candelas, or lux at one meter at the brightest part of the beam -- woops, no, the part of the beam providing the maximum luminous intensity. The "throw", as used by the FR reviewer, is the square root of that. So I'm measuring the square of the throw.
So is "brightness" the total luminous flux? When I defocus a light to convert a bright, woops, higher illumination beam into a dimmer, woops again, lower illumination beam, it's just as "bright" as before, even if I can take off my shades and quit squinting to look at it?
And is the FR fellow correct in his use of "throw" as the square root of the luminous intensity at the brightest part of the beam, woops, the part of the beam where the luminous intensity is maximum?
When I said my P1 was 9 times as bright as the L0P SE, I meant that its luminous intensity was 9 times as great, and that it has 3 times the throw. I'd guess that the "brightness" -- total lumen output -- is more like a 3 to one ratio, since the L0P SE has about twice the main beam diameter as the P1 but less spill. Hope that's clearer.
Thanks, I'm a real newbie at this, and have a lot to learn.
c_c