I like aa lights and wondering what a huge reflector on a lower powered light would do for throw. Thinking along the lines of 118mm reflector used in BLF gigathrower. Have a couple of Manker t01 that have listed throw of 282 meters. Any guess what a larger reflector would bring? A 2aa would look less ridiculous of course. Is there a point a larger reflector would be of no use?
Hmm, with an eliptical reflector and fixed focal point I believe there's no theoretical limit from linear optics alone, but that's useless. With a parabolic reflector there's clearly a limit somewhere below, not at, lumens/reflector_area being equal to 0.25 LUX (assuming you're really happy with the 0.25LUX definition of throw). But that's still enormous. The practical limit probably involves emitter size, optics quality etc... so I better leave it to someone with practical experience there.
Take the front area of the large reflector, divide it by the area of the small reflector, and multiply by the lux.
Then you will know how much it will throw.
So you could have 4 times the lux? How would that translate to throw?
4x lux = 2x throw
Seems like an idea to have a 2aa or 4aa thrower. And probably would not need a bunch of cooling fins that look kinda bad to me.
Lux at one meter presumably? So let's just say you replace it with a reflector of equal size. If the lux at one meter is presently 10 lumens/m^2.
Then you multiply 10 lumens/m^2 by 1/1 and get 10 lumens/m^2, which is not even a distance. I don't get your formula. Should I just assume a built in unit conversion and that becomes a throw of 10 m? That doesn't sound right.
In fact it should be approximately a throw of :
sqrt(10/0.25) or about 6 meters, because throw is the distance where lux reaches 0.25 lumen/m^2. Approximately, because inverse square gets a little funny if you're close to a large source.
Anything one thing is clear, you're saying twice the area is twice the throw. That's probably close to right, sounds kind of reasonable anyway. Doesn't it depend on the depth too? Is this assuming optimal depth for the area? This must be all worked out a 100 places, and maybe even correctly in a couple.
Yes, but it would start to seem fairly hilarious if you have a reflector the size of a frying pan, and only bother to power it with two AA's.
There are lights with 4aa and quite big reflctor
If you switch the LED to a dedomed XPG2 on DTP star you should get a nice throw
For example Nitecore EA41
Yes, if you want to stick to AA lights, then go for a 4xAA light. They usually have 40mm reflectors, which give pretty good throw. The Manker T01 has pretty good throw for a small 1xAA light, but you’ll get almost 3 times the throw with a 4xAA light. Get one with an XPL-HI LED, for best results. All the modern 4xAA lights produce around 1000 lumens or a little more.
The Convoy C8 will out-throw a 4xAA light by a little bit, due to it’s slightly larger reflector. I’m not aware of any 4xAA lights with a larger reflector than 40mm, but there’s probably some in a form-factor other than the soda-cans I have.
No, I said 4x the lux = 2x the throw.
The lux is proportional to the area.
This means that a reflector with 4x more area (and lux) than another reflector will get twice the throw in meters.
1/d^2 =4* 1/(2d)^2
You need to account for the center circle of the reflector though, since that is a blind spot that does not reflect LED light. This middle circle should not be included in the reflector front area.
doesn't say 4x the lux is twice the throw, but anyway I do agree with that, except not really, because of atmospheric issues, so it's less. So yeah, 4x the are should be 4x the lux, ok, so right, 4x area is twice throw. So twice the diameter is twice the throw.
By the definition of throw, which is 
Obviously real world is slightly less due to atmosphere.
And btw, it is not exactly 2x diameter = 2x throw, I specifically said 4x area because the center circle of the reflector does not count.
You might have 2x diameter, but that does not mean the front area will be 4x once you subtract the circle.
Circle's not huge, but yes.
I don't think NIST dictates definitions of flashlight throw and probably never will, and the best you have is ansi, which much be purchased which already makes it non-academically authoritative in my opinion (it's a business standard), but they don't seem define "throw" either in the official doc (which i can only find the table of contents for because it's for pay), but only "beam distance".
In their wiki page overview they says beam distance is:
"The distance in meters at which the flashlight produces a light intensity of 0.25 lux. This is not very bright, about equal to a full moon. This distance is not actually measured. Instead the value is calculated (approximated) by taking the peak beam intensity measured above, dividing by 0.25 lux, and taking the square root of the result. For example, the Quark AA has a peak beam intensity of 1,622 cd. Divide this by 0.25 to get 6,488. Now take the square root to get 80.55. This agrees with the value on the packaging, which is rounded to 81 meters."
Scratch out is mine. So they first define a term and then a standard approved way to approximate it. Hardly black and white. Yes, the quoted approximation is defined in the way you say.
It doesn’t have to be .25 lux, you can calculate the distance to 1lux if you want, or any other value.
The point is, that whatever value you choose, if you have 4x the area then you will get 2x the distance.
I do Have a Nitecore 4aa with a XPL HI led. Just wish someone would put a seriously big reflector on one.
Thanks this is very informative stuff.
What is the benefit of using AAs when the light is large anyway?
There is actually a point where a large reflector is of no use. The important thing here is the ratio between the diameter of the light source (the LED) and the diameter of the reflector. You only get a higher luminous intensity (=>throw) with a larger reflector if it’s completely lit up by the light source (looks at Enderman’s picture => the reflector is yellow everywhere => this is important). The bigger the reflector becomes when using the given light source the more precise the parabola shape needs to be.
The best example of this is the Maxabeam. It has the same size reflector as the BLF GT, but a much smaller light source. The bright spot inside the arc of the Xenon bulb has a diameter of around 0.125mm. Only when the entire surface of the reflector is lit up by this tiny spot in the arc, will the light have 12Mcd. Because of this the Maxabeam has an electroformed precision reflector.
The Die of the Cree XHP-35HI in the BLF GT has a “diameter” (distance from corner to corner) of 2.9mm (size measured here), 23x as much. So the reflector doesn’t need to be as precise as the one in the Maxabeam.
LED flashlights usually don’t have this problem because most LEDs are rather large (optically speaking). Common cheap aluminium reflectors are easily good enough for them.
Use aa and aaa nimh exclusively for all my devices except smoke detectors.
You would need 16 NiMH AAs for one hour of runtime with the GT ;).