Same Reflector: Different LEDs - Is Beam Spill the same size?

SCEMan

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I've always wondered about this but no longer have the lights to test this question...

If the exact same reflector (assuming LED opening is only change) is used by different LED types, how, if at all is the diameter of the beam spill affected? Or is the reflector the determining factor regardless of LED used? Not talking brightness, but size/diameter of the beam spill.
 

Canuke

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Since the spill cone is basically the "direct from emitter" light, I'd expect beam spill angle to remain the same, given identical positioning. Spill edge sharpness will vary with emitter/die apparent size.
 

FRITZHID

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All things being equal, aside from LED die size, (I.e. Both 5 watts but one die is 2mm² and the other is 4mm²,) the smaller die will throw significantly farther, assuming same efficiency.
 

swan

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Just did a quick comparison with my two Olight M2X-UT,s one with a xpg2 dedomed, the other with a xpl hi intensity and they have the exact same size spill/ diameter,but with less intensity in the xpg2.
 

THE_dAY

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Just did a quick comparison with my two Olight M2X-UT,s one with a xpg2 dedomed, the other with a xpl hi intensity and they have the exact same size spill/ diameter,but with less intensity in the xpg2.

Swan, thanks for the real life comparison, appreciated!
 

Timothybil

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All things being equal, aside from LED die size, (I.e. Both 5 watts but one die is 2mm² and the other is 4mm²,) the smaller die will throw significantly farther, assuming same efficiency.
Yes. To explain: the ideal light source for a parabolic reflector would be a point source located at the focal point of the reflector. In that case ALL of the light emitted that reflects off of the surface of the reflector would leave the reflector in parallel rays, resulting in a tight beam with the only spill being caused by the few rays not being reflected by the reflector. (Say that three times fast!) But since all practical light sources are larger than a single point, there will always be rays that reflect off of the reflector surface in such a way that they exit not parallel to the beam, resulting in spill. The larger the emitter surface, the more rays exit off-axis, and the more spill, for a given reflector.
 

TEEJ

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Spill is the unfocused light that MISSED the reflector, so, if the DEPTH of the LED's emitting surface was the same, and it was not tucked in more, or less, in the bowl...then the spill, missing the reflector, should be at least similar.

The width of the LED would change the initial emission point at the edges of the LED for example, so that could produce an example of a change...and change the spill too.

The beam width would be drastically different though, as the corona and hot spot are also very very related to the LED's relationship with the reflector.

The WASTED light would be potentially similar, but brighter or dimmer, or wider or narrower, depending on the LED's output, and LED surface area...and the spill IS the wasted light.


If you want "spill" it typically means you are using the wrong beam angle for your use...but are so used to not having the right beam angle, its how you compensate for always having the wrong light for the job.

:D
 
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scs

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Spill is the unfocused light that MISSED the reflector, so, if the DEPTH of the LED's emitting surface was the same, and it was not tucked in more, or less, in the bowl...then the spill, missing the reflector, should be at least similar.

The width of the LED would change the initial emission point at the edges of the LED for example, so that could produce an example of a change...and change the spill too.

The beam width would be drastically different though, as the corona and hot spot are also very very related to the LED's relationship with the reflector.

The WASTED light would be potentially similar, but brighter or dimmer, or wider or narrower, depending on the LED's output, and LED surface area...and the spill IS the wasted light.


If you want "spill" it typically means you are using the wrong beam angle for your use...but are so used to not having the right beam angle, its how you compensate for always having the wrong light for the job.

:D

I think the reflector also puts some light into the spill, like Timothybil described. Spill does not consist of only light that misses the reflector.
 

SCEMan

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Okay, much good information here. The consensus sounds (to me) like the total diameter of light produced (beam+spill) from a given reflector would be consistent when used with different LED types (assuming depth of emitting surface is the same).

That's fascinating - an MGT-2 and XP-E would have the same diameter of total light output. Although I doubt an XP-E LED would focus in the reflector opening needed for an MGT-2 LED.

Is there a practical term for a flashlight's light output (beam+spill)? I see beam and spill used interchangeably in posts.
 

Timothybil

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There are two measures of light output used in flashlights. One is lumens - the total amount of light emitted by the light, regardless of which direction it is going. A bare ten lumen light bulb will shine in a small area all around the bulb, while a ten lumen flood bulb will shine much farther in the direction of the flood, but nothing at all in other directions. Yet both are putting out ten lumens.

Candela (cd) is the measure of the amount of light striking a given spot. In the above example, the bare bulb might be measured at 20 cd, while the flood bulb might be measured at a hundred. (Numbers picked out of the air for example only and have no basis in real life) Candela is usually specified for the brightest spot in the lamp output, so for a given lumen rating, the higher the candela reading the more light is being concentrated into that spot, and thus the further that light will 'throw' in that direction.
 
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