what makes a flashlight throw.

I was comparing my Pelican M10 to the Scorpion. The M10 seemed to have a spot far away where you could see just light at the same target from the scorp.

larger (and better) reflector, smaller point source, tight focus with little divergence, lotsa lumens... /ubbthreads/images/graemlins/icon3.gif

Lumens make no difference, it's surface brightness of the source, so short arc is #1 (60 times hotter than halogen), HID is #2 (4 times hotter than halogen).

Larger and better reflector is also important, since with a large enough reflector a Halogen will out throw the Maxabeam.

Tight focus? I can't figure that one out. Shallow versus deep reflectors? Shallow throws better, but it has more spill. I'm confused here. I think it's surface area of the reflector.

I understand what you mean but lumens does make a difference...
It might be one of the less important factors but then again, some people compared a M3t HOLA against a MG85 with a smaller reflector and the lumens difference did show.
Oh and about the tight focus thing, I'm not sure either. Some reflectors seem to be designed to focus a wider hotspot while others will focus down to a much smaller spot. In this case, it's not a problem of size; the Pr reflector seems to perform better than some others reflectors of the same size. The SRTH reflector throws better than the 3" T series reflector. Again, /ubbthreads/images/graemlins/icon3.gif

Lumens makes the beam wider, but not put more light intensity on a target. But I agree, lumens is what most people want (it's like rating cars, people buy horsepower, but prefer torque).

M3T HOLA versus MG85, which one won? I'm not sure which one has less surface area?

IIRC, the Mag85 with its smaller 2" carley reflector outthrows the M3t with the larger 2.5" millenium turbohead by a large margin.
Although the spot size was a lot bigger, intensity at the center was also higher because the lumen difference here was pretty big so maybe it's a bad example but proves that higher lumens rating does matter.

Throw is a function of light source output (lumens) the size of the source, the diameter of the reflector, the depth of the reflector, and the shape of the reflector.

The size of the source and the diameter of the reflector determine the size of the hotspot. Larger reflectors and smaller sources will result in smaller hotspots. All else held equal, a smaller hotspot will result in more throw as light from the source will cover a smaller area.

The depth of the reflector and output of the source determine the brightness of the hotspot. A deeper reflector captures more light from the source and will result in a brighter hotspot.

The shape of the reflector can effect both hotspot size and brightness. Design tricks can be used to optimize a reflector to a source of a given size (resulting in a brighter hotspot) and/or to increase the size of the hotspot.

Throw depends,...

NOT on lumens,...

BUT on surface brightness of the source, short arc, then HIDs (and their permutations) and then Halogens (the more overdriven then better). It's all a function of surface brightness of the source.

And actually, IIRC, a shallow reflector will give a tighter hotspot since it's a segment of a "larger parabola" while a deeper reflector (part of a smaller parabola and thus increasing the source to reflector ratio) will give a bigger hotspot.

Design tricks for reflectors are great, but in general HIDs and halogens have similar hotspot sizes so it doesn't matter. Maybe for a short arc.

Agreeing with cheese 100% on this one. Lumens don't really matter worth a darn. Although, it sure makes things look more impressive /ubbthreads/images/graemlins/icon3.gif

Don't forget that you have to factor in efficiency of all the bits and pieces. In the Mag85/M3t situation, it is a possibility that the Mag85 reflector is much more efficient than the M3t's reflector. That would sure help anyway.

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cheesehead said:

Tight focus? I can't figure that one out. Shallow versus deep reflectors? Shallow throws better, but it has more spill. I'm confused here. I think it's surface area of the reflector.

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A deep reflector will catch a larger fraction of the emitted light and project it into the hotspot, at the expense of a narrower sidespill cone. Often a shallow reflector (like the ones found in lanterns) will throw better, but the relevant factor here is the gentle curvature of the reflector rather than its shallowness.

The general trend is that you get a tighter beam if the light emitter is made smaller, or if the radius of curvature at the base of the reflector is made larger.

reflector shape is key. There are differenct shapes, not just "shallow" and "deep". Geometry cannot be avoided here, folks. Mag gets it's throw by using a smooth, parabolic reflector, maximized for throw.

I was already assuming a parabolic reflector, which is what most flashlights use anyway. It is possible to characterize the overall shape of such a reflector by its focal length (1/2 the radius of curvature at the base) alone. The spatial extent, which is specified by either width or depth, will determine what fraction of the emitted light is collected into the beam.

Lol!
Guys, what I meant was a trivial point! You see how you can see better with a P60 lamp than one of these older 2D flashlight? I wasn't refering to how to make the light you have go further in front of the light but how you'll end up with more light further if you had a lot more light to start with...
Take two lights with the same le and reflector but one set on low; the brighter is likely to reach further.
I frankely don't see how the carley 2" reflector is superior to the SF 2.5" reflector... that was just testing lights in different classes; again, not very fair.

I think that bulb possiting in the reflector is also essencial.

Cheesehead is absolutely right:
If you assume perfect focusing and reflectivity and so on, the maximum lux reading (=throw) depends only on the reflector diameter and the surface brightness of your emitter.
It is very simple: If you look into the reflector, you see everywhere the same brightness (a mirror can't increase the brightness of the source) and the Lux reading is therefore proportional to the reflector cross sectional area at the lens and emitter brightness.

The depth is unimportant for the lux reading (and therefore throw). A deeper reflector collects more light, but the the added light is used to increase the spot diameter.

Assumptions for my statements: lambertian emitter (=same brightness in every direction) and parabolic reflector, well focused source and no angle dependendance of the reflectivity of the reflector.

Just a basic question, but how is "surface brightness of the source" measured? What are the units? Thanks.

the beakman

Sorry, double post.

Never before have I heard such wrong info (with minor exceptions).

The unit is lambert: la=10/Pi*cd/m2.

I'm not a expert for measuring the brightness. If you know the area you could use a normal lux reading and calculate it, but maybe there is also a method to measure it directly (similar to a pyrometer) ?

You might also check lamberts cosine law.

By the way lambert was a german /ubbthreads/images/graemlins/smile.gif

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turbodog said:
Never before have I heard such wrong info (with minor exceptions).

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unfortunately, he didn't enlighten the rest of us with his brilliance /ubbthreads/images/graemlins/jpshakehead.gif. Well that's one thing we can be thankful for! /ubbthreads/images/graemlins/happy14.gif