The Real Reason for Throw - an in depth examination

[dymonite69]

But so far it seems that I've been out-voted. :shrug:

Well I don't you will ever have a sufficient quorum to determine this. Language tends to be fairly dynamic - English particularly so. It is evident by the expanse of dictionaries over the decades.

But the OP (I only just worked out this meant original poster) uses words like collimation and parallel rays so it does imply directing the lighting power.

Examining the etymology of the word and its common use also suggests energy is being projected in a direction. Contrast this with 'flood' where a substance is distributed in many directions to fill up the available space.

He also points out that raw brute power lumens does not automatically equate with throw. Judging from other threads I don't think that the mature CPF community would dispute this. A lanky pro baseball pitcher could throw further than a pro powerlifter. But later we rule out the sun and aerial searchlights as unfair comparison. But I note someone here has produced an elegant hand-held 10W HID with a custom fabricated reflector that projects the beam some 500 yards. So is this a fair comparison with a 10W LED SSC P7 but a 35W HID isn't? :shrug:

 

[the_guy_with_no_name]

The following is an informal (and probably incomplete or incorrect) proof. I ask that you all evaluate the assumptions and conclusions I make:

First, two important starting points:
1. Not all light is visible (such as infrared). For the rest of this post, "light" means "visible light."
2. Since photons don't have mass, we cannot use the regular definition of density to measure them in a given volume. Instead, we have to use the number density. But, since I don't like the phrase "number density," the rest of this post uses "density" to refer to "number density" when talking about photons.


- Light is made up of photons.
- For any given volume, more photons equal more light.
- Using substitution, this means that a higher photon density equals more light.
- Brightness is the visual perception of and directly proportional to the amount of light.
- Using substitution, brightness is the same as photon density. In other words, higher photon density is the same as "brighter"

Since humans cannot see all photons, and since counting the total number of photons is practically impossible, instead of using the term photon density, I will use the term lumen density. That is, the measurable number of lumens in a given volume. This is an important "turning point" in the discussion because the measure of luminous flux is not constant with the number of photons present. This is due to the fact that luminous flux is a weighted sum of the visible wavelengths of light and does not count photons outside of the visible range.


This brings me to the conclusion that brightness is a perception of lumen density.

If this is correct, then "throw" as it has been popularly defined so far would simply be the lumen density at a given distance. In other words, brightness at a distance.

Those of you who champion this definition should realize that any light source will be able to "out throw" any other unchangeable light source, regardless of focusing apparatus, based purely on total number of lumens.

It was kind of making sense until the last statement.

Those of you who champion this definition should realize that any light source will be able to "out throw" any other unchangeable light source, regardless of focusing apparatus, based purely on total number of lumens.

This statement is incorrect as is.

If you want to add some clarity such as

any light source of given surface area will be able to "out throw" any other unchangeable light source with equivalent surface area, regardless of focusing apparatus, based purely on total number of lumens.

it might come a little closer.

And yet again, we are now talking about surface brightness....
(are we not?)

...already discussed in this thread.

but I can not guess what you are trying to say

tgwnn

 

[the_guy_with_no_name]

dymonite I agree with everything you said, up until this point:

...but the current definition of throw makes no mention of how the light from the light source is being directed. Indeed, the definition could apply to a totally omnidirectional light source like the sun.

I don't really like the current definition specifically for this reason. I also think that a correct definition of throw needs to involve wording like "the majority of the light energy being emitted by the source" as you said. But so far it seems that I've been out-voted. :shrug:

Many folks actually agree with you and this is reflected in the earlier definition/posts in this thread.

It is worth noting that as an extreme example
in a very poorly positioned emitter/reflector combo,
the majority of light
may never even bounce off the reflector
yet, enough may bounce enough (let's say 35% of the light)
to make it a good thrower

The current definition of throw in this thread expressly states "enable identification of distant objects"

the light above could still acheive this
floody lights could still acheive this

please note however, we have been defining throw not thrower

TRUE
a thrower can throw

FALSE
only throwers can throw

So to maintain simplicity and accuracy, "project & beam" may be best left out of the definition of "Throw".

A "Thrower" could be defined as "A flashlight designed primarily for throw".


Now we might consider adding

"A narrow beam flashlight designed primarily for throw....." but is it neccessary?

Is it possible to have a broad beam (dedicated) thrower?

tgwnn

 

[ss Dragonfly]

Use a thicker piece of wood and go slowly and with half the pressure you think you should....it has given the best results for me. Good luck.

Cheers,
Shane

 

[dymonite69]

A "Thrower" could be defined as "A flashlight designed primarily for throw".

Now we might consider adding

"A narrow beam flashlight designed primarily for throw....." but is it neccessary?

Is it possible to have a broad beam (dedicated) thrower?

Perhaps:

Thrower - a flashlight designed to maximise the ability to visualise distant objects?

This makes no assumptions about how the designer wishes to achieve this objective.

 

[mudman cj]

Use a thicker piece of wood and go slowly and with half the pressure you think you should....it has given the best results for me. Good luck.

Cheers,
Shane

How should the piece of wood be used?
:whoopin:
Sorry - in the mood for some humor this morning.

 

[LuxLuthor]

How should the piece of wood be used?
:whoopin:
Sorry - in the mood for some humor this morning.

Yeah, I can't wait for Master Dragonfly's next contribution. I'm thinking it must have been a koan to bring the discussion to an end. Brilliant!

 

[the_guy_with_no_name]

Use a thicker piece of wood and go slowly and with half the pressure you think you should....it has given the best results for me. Good luck.

Cheers,
Shane

The thicker piece of wood did the trick (if not but for a brief moment).

In lieu of the thicker wood, there was no space for batteries so I ran a wire directly to the mains.
This resulted in a brilliant momentary burst of light, that according to radio reports could be seen for miles.
The pressure however actually increased after the initial burst and suddenly it was dark.

Am I doing something wrong?

tgwnn

 

[HarryN]

Remember that NEMA (National Electrical Manufacturers Association) Flashlight Basic Performance Standard report (that some of us bought for $60)? Table of contents here.

Well without violating my copyright agreement, they did establish a standard for testing "Beam Distance" & "Peak Beam Intensity" out the front of the light which is really designed to accurately quantify what we are talking about as throw. Their methods are exceeding simple, but hit the nail on the head.

It does involve using a light meter at certain distances and some square root algebra. The light meter using the CIE curve address the issues of color.

Sorry to be coy, but if you buy a copy you will see why it behooves one to be compliant.

Thanks for that link

 

[jcw122]

I have a question, since the XP-G emitter is larger than the XP-E...is this why people are saying the XP-Gs don't have as much throw as the XP-Es? Thanks.

 

[easilyled]

I have a question, since the XP-G emitter is larger than the XP-E...is this why people are saying the XP-Gs don't have as much throw as the XP-Es? Thanks.

Its back to surface brightness which is lumen output divided by surface area.

However much bigger the surface area of the XP-G die is than the XP-E die, then the XP-G would need to output that same degree more in terms of lumens than the XP-E (in the same light) in order to throw the same.

I assume that it doesn't achieve this, but I have to confess to lacking in knowledge about the exact die dimensions of the XP-G and XP-E and predicted outputs between the 2 for given currents and being to lazy to look it up.

 

[gcbryan]

This is a sticky but the first post isn't completed and hasn't been updated since March?

Is this a dead project/thread now?

 

[saabluster]

This is a sticky but the first post isn't completed and hasn't been updated since March?

Is this a dead project/thread now?

No this is not dead. I am just spending most of my time here working on my next light. Once that is done I will be coming back to this thread.

 

[Walterk]

I found my definition of throw in this almost forgotten thread: Proposed new standard for measuring flashlights
Beware that the definition of a 'thrower' should be different from that of a 'searchlight'.

 

[Lord Bear]

I am if nothing else, FASCINATED. This thread has enabled me to understand a thing or two. I will not contribute as in the first post stated, I really have nothing to contribute to ADD to the knowledge. But this thread is very illuminating. (Pardon the pun.) Thank you and please soldier on!

 

[gcbryan]

Can someone definitely answer this question...when using a reflector (let's assume with a XR-E R2) what does greater reflector width determine...intensity of the hotspot (when the emitter is kept the same)?

Does greater reflector depth determine the narrowness of the hotspot (in additional to limited spill by capturing more of the beam)? Again assuming the emitter is kept the same.

I'm trying to keep the surface brightness and size of the emitter out of this question. I just want to know exactly what effect greater reflector width and depth have.

 

[red02]

I think that it's impossible to ignore what type of emitter you use when you ask about reflectors. Each reflector is custom made for the emitter. A XPG reflector will not work well with an XRE and vice versa.

From my limited understanding, the greater the surface area of the reflector, the more throw. As the emission angle decreases, the reflector's diameter decreases and its depth increases to maintain the same throw. I could be completely wrong of course.

 

[saabluster]

Can someone definitely answer this question...when using a reflector (let's assume with a XR-E R2) what does greater reflector width determine...intensity of the hotspot (when the emitter is kept the same)?

Does greater reflector depth determine the narrowness of the hotspot (in additional to limited spill by capturing more of the beam)? Again assuming the emitter is kept the same.

I'm trying to keep the surface brightness and size of the emitter out of this question. I just want to know exactly what effect greater reflector width and depth have.

You are asking very difficult questions as the answer depends on all the factors involved such as your starting point in diameter. Widening a reflector in one instance may mean more throw and in another less even if you specify a single LED. There is no one-size-fits-all in this regard and I'd encourage you to stop looking for it as you will just get frustrated.

I don't have the time to lay out all the various scenarios for you unfortunately. I will say that if you fully and truly understand the principles I laid out about the reflecting surface distance most of your questions would be answered. Increasing the diameter or depth both accomplishes the same goal of moving that reflective surface farther away from the source.

Does greater reflector depth determine the narrowness of the hotspot

Yes and no. Like I said it depends on the factors. For instance take two reflectors both of which have both the same diameter and depth. One can have a large hotspot and one a small hotspot. How can that happen when both those two specs are "locked"?

Remember that the hotspot is formed with light that comes from all up and down that reflector not just the rim.(no need to go into this in detail but some may consider the relatively weak light they see on the outer portion of the beam to be the corona rather than the hotspot. LEDs are not as prone to this as HID due to the characteristics of the emitter itself and the variance of luminance seen in the arc vs the consistency seen across the LED die)

The diameter of the top rim does matter but as you come closer towards the source the projected beam from those parts are wider. Therefore if the reflector is of the type where it is a cone all the way down to the LED then it will have a wider hotspot than it otherwise could. I'm sure you have seen those reflectors that come down and then have a large flat area that surrounds the LED. The reason you see reflectors like that is because the designer wants as much of the reflective surfaces to be as far away as possible. There are practical limits to this of course. The result of this though is that even the light reflected at the lower regions are relatively far from the source and the resultant beam as a whole is smaller. You've heard the saying that a chain is only as strong as it's weakest link? A beam is only as small as it's largest part.

 

[saabluster]

From my limited understanding, the greater the surface area of the reflector, the more throw.

It is not about just surface area. You could have an extremely wide reflector with huge amounts of surface area but if the depth is not there you will not be collecting much light. It is a balance of all the factors that matters not a focus on only one.

 

[gcbryan]

I think that it's impossible to ignore what type of emitter you use when you ask about reflectors. Each reflector is custom made for the emitter. A XPG reflector will not work well with an XRE and vice versa.

From my limited understanding, the greater the surface area of the reflector, the more throw. As the emission angle decreases, the reflector's diameter decreases and its depth increases to maintain the same throw. I could be completely wrong of course.

It's not impossible to ignore what type of emitter you use when you want to understand reflector "theory". I'm not asking for help to pick out a reflector for a particular application.

I'm not sure but I think it's not totally about surface area either. I say this only because if you get more area by decreasing diameter and increasing depth this works only by redirecting spill to the hotspot and this works best only if you have an emitter like the XR-E with a 90 degree beam.

If you have something like the XP-G there is much less spill to redirect and therefore a deeper reflector would not offset the gains lost from a wider diameter.

Correct me if I'm wrong. Increasing width is putting the same amount of light into a tighter spot thereby increasing brightness.

Increasing depth is putting more light into the same spot thereby increasing brightness. If there is less (or no) spill then increasing depth does nothing as there is nothing or little to redirect.

Consider the case of an aspheric lens rather than a reflector. Increasing diameter does the same thing as increasing diameter in a reflector. Since there is no spill there is no counterpart to increasing depth.

There is another variable with optics however...focal length and this is a trade-off between short and more light gathering and longer and a tighter but dimmer hotspot.

With a reflector varying the depth does nothing regarding the size of the hotspot.

Edit: Saab, I didn't know you were responding. I guess we were both typing at the same time.