Why can't LED match incandescent in throw?

[enLIGHTenment]

You have to remember that leds are emitters; that means they are projecting the majority of their output forward, missing the reflector with much of it. This is why optics are used instead.

The data do not support this. Of the ten most throw effcient (most throw for lowest output) LED lights covered on FLR, nine use reflectors. The only one to use an optic is the KL3.

More significantly, Diamond's D-cell Mag mods, which use unmodified Mag reflectors, have essentially the same throw efficiency as a stock Maglite. The only reason a Terralux 3 cell mod doesn't throw as far as a 3D cell Mag is that the Terralux puts out only 2/3rds as much light.

 

[Luna]

Optics are necessary due to the source/aperature ratio. Decrease the die size, the smaller the reflector needed.

Optics work on a different principle thus are less dependent on size.

With a high temp TIR, you can possibly get large the likes of an H4 to throw like a HID

 

[asdalton]

Big reflectors don't help LEDs as much - they don't have the full 360 degree radiation for an even beam, and optics loses even more energy. But worse, because it is virtually a point source, its light is already diminished by the time it reaches the reflector. In comparison, the filament in the incan bulb has a much larger radiating surface, so it can enjoy the 'conservation of radiation" further.

In general, the best light reflectors will have a radius of no more than 5x the filament length.

I'm not sure where you're getting this. For throw, big reflectors are better, period. And smaller light sources are easier to focus into a tight beam. Many of us who have done mods can confirm this fact first-hand.

 

[Builder]

I'm not sure where you're getting this. For throw, big reflectors are better, period. And smaller light sources are easier to focus into a tight beam. Many of us who have done mods can confirm this fact first-hand.

That's exactly what I said:

a larger reflector will ALWAYS outperform a smaller one, given similar lights

But LEDs benefit less than incans because their radiation starts experiencing the Inverse Square law almost immediately.

Imagine a 2-feet wide reflector around a 3W LED. Do you think it will put out substantially more light than a 6-inch one? How about a 5 feet one?

Fact is that conventional LEDs reach a performance limit quicker than a light bulb of the same lumens.

 

[asdalton]

But LEDs benefit less than incans because their radiation starts experiencing the Inverse Square law almost immediately.

Imagine a 2-feet wide reflector around a 3W LED. Do you think it will put out substantially more light than a 6-inch one? How about a 5 feet one?

Fact is that conventional LEDs reach a performance limit quicker than a light bulb of the same lumens.

The inverse square law is not a primary; it is a consequence of the conservation of photons through any enclosing shell or solid angle regardless of distance. Once the distance becomes large enough that the viewed profile of the light source is no longer changing in shape with increasing distance (though it continues to get smaller), then the inverse square law applies to the illuminance along any ray.

If a small and large reflector both subtend the same solid angle around a light source, then they will catch the same number of photons. The difference is that the larger reflector will have a smaller divergence angle, due to the smaller ratio of emitter size to source-reflector distance. Such a beam does not contain more light, but it will be tighter and have a larger useful reach.

 

[Builder]

The inverse square law is not a primary; it is a consequence of the conservation of photons through any enclosing shell or solid angle regardless of distance. Once the distance becomes large enough that the viewed profile of the light source is no longer changing in shape with increasing distance (though it continues to get smaller), then the inverse square law applies to the illuminance along any ray.

If a small and large reflector both subtend the same solid angle around a light source, then they will catch the same number of photons. The difference is that the larger reflector will have a smaller divergence angle, due to the smaller ratio of emitter size to source-reflector distance. Such a beam does not contain more light, but it will be tighter and have a larger useful reach.

Are you saying then that if I use a parabolic reflector with a single LED as a point source then the light will travel indefinitely?

 

[asdalton]

Are you saying then that if I use a parabolic reflector with a single LED as a point source then the light will travel indefinitely?

Light always travels indefinitely, unless there is something to stop it.

The important question is how to put a useful illuminance (lux) on a target some distance away, given a light source of finite total output (lumens). For that, a less diverging beam gives you more illuminance at a given distance, or more distance reach for a given illuminance. And to get a less diverging beam, you need to use a larger reflector, or else use a smaller light source with the same lumen output.

 

[lambda]

Re: Why can't LED match incandescent in throw? - They Can!

LEDs can throw:

Here's the barn lit up with LED goodness from well over a hundred yards away.

How do we get such light output from an LED? Big *** reflector and Luxeon V side emitter driven to 1.4 Amps.

LEDs can throw some serious light if in the right configuration.

So, in summary, LEDs can throw...

 

[Handlobraesing]

Re: Why can't LED match incandescent in throw? - They Can!

So, in summary, LEDs can throw...

But, can that same LED give a throw equal to or greater relative to an incandescent making the same amount of total output? That is the entire point of this discussion.

 

[270winchester]

Re: Why can't LED match incandescent in throw? - They Can!

But, can that same LED give a throw equal to or greater relative to an incandescent making the same amount of total output? That is the entire point of this discussion.

I say you could.

A E2e with MN03 makes 80+ lumen and regeister around 1100 lux at one meter, runs for 75 minutes or less. That's on two cells.

A McLux PD III with McR20 gives 1100ish lux at one meter, runs on one cell, 500 mAh to the emitter for 90 minutes.

I suspect a 2 cell ALeph 2 running a DB917 with spank the E2e in throw with longer runtime.

How well you can see the projected is a whole other can of beans.

P.S., 400+ posts in two months? wow.

 

[enLIGHTenment]

Re: Why can't LED match incandescent in throw? - They Can!

But, can that same LED give a throw equal to or greater relative to an incandescent making the same amount of total output? That is the entire point of this discussion.

See posts #14 and #21....