The Real Reason for Throw - an in depth examination

[McGizmo]

Re: The Real Reason for Throw-an in depth examination

Somewhere I have an old lux meter that was probably made before I was born (I am over half a century in years). With it is a small booklet defining minimum lux for various activities and work types. I assume this meter was for electricians and lighting specialists to aid them in determining whether ambient light was sufficient for the task at hand. In other words, it was a tool to aid them in establishing whether there was enough light thrown on the field of interest. Something else to consider with a flashlight though is that you are not necessarily close to the object being illuminated and typically you and the source of light are equal distant from the object of illumination. You can't see an object unless it is reflecting enough light back to you for your eyes to perceive it adequately. 10 lux hitting an object at 20 feet from you might be more than adequate but 10 lux hitting an object 100 feet from you may not.

I think as others have suggested, a higher flux source (higher lumens) even with poor collimating may do a better job of illuminating a distant object if the landscape itself bounces some of those photons down field and off the object to reflect back to you. A simple example of this is a white room with a ceiling bounce. Flux is more significant than lux in regards to illuminating an object in the room. Only the photons that you release which come back to you can tell you what is out there. They have to hit the target directly or indirectly from a bounce (or many) and then come back to you.

Throw is about delivery of light to a distant target. Seeing the target is about the return of light bouncing back to you from the target. How you accomplish throw and perhaps define it is what I assume this thread to be about.

How you maximize your return on sent photons can be a function of throw but can also be a function of other parameters and considerations. If I suggested that a 50 lumen flood beam could do a better job of illuminating a person 100 yards away from you than the tight collimated beam of 250 lumens you have in your hand, you would likely question my sanity. If I were to further qualify my comment in stating that the 50 lumen flood beam was positioned 5 feet in front of the person....... :duck:

Since the original post in this thread is going to be updated with the real meat and these further comments more like foot notes hopefully they can be accepted as they are whether on target or off tangent.

Stepping back a few years in CPF, there was a time when all of the modders and active members were focused on lux and even to the point where photos of a lux meter with its measure were included in posts. I would suggest that as the LED's got more efficient and delivered greater flux, this practice was relaxed as people started to realize that they could deliver enough light down field in many cases without the need for maximum collimation.

What is more important? How bright a flashlight is or how bright and effectively the target being illuminated by the flashlight is? Lumens tell you no more about throw than lux tells you about flood.

 

[saabluster]

Re: The Real Reason for Throw-an in depth examination

Please do not quote me out of context.
Kindly note, I already stated what you are stating and agree with you on the above
Are you saying that #1 below is not a fact?

#1
#2
the keyword being seems.

I am only hoping to add clarity, not introduce any new concepts.

btw,
I think your first post was awesome!



tgwnn

For some reason when I quote you it comes out all garbled. #1 is correct. Not sure what you mean by #2. The SST90 doesn't seem to out-throw anything. It is just an LED. Do you mean the SR90?

 

[MustardMan]

Re: The Real Reason for Throw-an in depth examination

I definitely agree with some other posters that as specific as possible a definition of throw is needed to help clarify what you mean. As its simplest, higher lux at a given distance equates to better throw, but from a subjective point of view, that might not be interpreted as "better" throw by an onlooker. As an extreme example, a laser produces massive lux in a very small spot, so by that definition it is throwing like crazy, but no one would call that a good thrower, because it's not use-ably illuminating the target.


An earlier poster made the observation that, due to the ambiguity of the term "throw", a slightly lower lux value that illuminates a target at a given distance with a wider hotspot could be considered "better" throw from the standpoint of illuminating the target better.

Put another way - if you get far away enough that one light has a very dim, but small hotspot, while the other light has a much larger, but only slightly dimmer, hotspot - the eye might be able to pick out the slightly dimmer one better than the brighter one. A casual onlooker might interpret this as "better" throw.


I personally think it's too difficult to include such subjective ideas into the definition of throw, and so such ideas should be discarded, but it might be worth defining throw in as precise a fashion as possible, to eliminate such interpretations from the outset, rather than letting that ambiguity muddy the discussion.

 

[the_guy_with_no_name]

Re: The Real Reason for Throw-an in depth examination

In furtherance to my last post I should add that the reason that the SR90 can out-throw lights with a higher surface brightness is due to the reflector. The outer portion of the reflector is farther away and therefore the resulting beam has less divergence because that part of the reflector "sees" a smaller source.

Again, I completely agree with you

tgwnn:
In a perfect world, considering All factors are the same, the emitter with the highest surface brightness will ALWAYS out-throw an emitter with a lower surface brightness.

Please recall I stated "considering all factors are the same".
There is no ambiguity with why I stated ALL, rather it was a deliberate choice.
Hence I was only refering to the difference of emitter surface brightness and not emitters in flashlights with different sized reflectors/lens/coating etc.

Purposely, I hoped to maintain the asthetic bliss of your first post and keep it simple and concise (as per your request) hopefully adding value, without discussing the theory behind my statements in details or address other posts (whether they are acurate or not) or link to reference information.

Does that add clarity?

I appreciate your feedback and do feel free to correct anything that is factually wrong or detrimental to the CPF community or not inline with your thread.

thanks muchly
tgwnn

 

[copperfox]

Re: The Real Reason for Throw-an in depth examination

First of all, does the OP of a thread have the authority to decide who gets to post in the thread? This begs the question: who is the owner of a thread; the original poster, the community as a whole, or the person *cough* Greta *cough* paying for the server and bandwidth?
A good topic for another thread, I think.

On topic, I think that this is a great thread, so lets keep it going. While pondering this subject it occurs to me that there is a difference between absolute (measured) throw, and the perception of "throwiness". Let me explain what I mean using the following example.

Standing a fixed distance from a white wall, you point a flashlight using an MC-E emitter at the wall straight ahead. This flashlight has a very wide beam pattern (something like the Malkoff M60 MCE). For the sake of argument let's just say you measure the lux at the white wall to be 200 lux. Now turn on a flashlight using a low powered single die emitter and a narrow beam secondary optic (something like the Malkoff M60LL with 8 degree optic). Now you measure the lux again and find it to be 190. (This is only an example and may not reflect real life).

The result of this mental experiment is to show that a flashlight that appears to be have poor throw (aka "floody") can, in an absolute sense, throw better than a flashlight that has a much narrower beam (200 > 190). In contrast, if you asked a layman which light is "throwier," the answer would usually be the light with the narrower beam. However, what I'm trying to express with this example is that the absolute definition of throw, as being lux at a certain point (candlepower) is NOT sufficient! Instead, the perception of throw can in many cases be more important than numbers. Discouragingly, it would appear that this revelation has now made it impossible or at least very difficult to come up with a definition of "throw," because we all know how variable and tempermental human perception can be. You cannot simply rank flashlights from greatest lux to lowest; this will not give you an indication of how "throwy" a beam is. Despite the difficulty of quantifying human perception, I think a reasonably good definition can still be found. Therefore I submit the following:

A flashlight's "throw" in a perceptual sense is directly proportional to the percentage of its total output that is collamated to zero degrees straight ahead.

The key phrase here is "percentage of its total output." So for the MC-E in the example, although it may have a higher measured lux on some given target, a lower percentage of its total output is contributing to that center lux reading, while with the XR-E, more of its total output is contributing to the center lux reading.

The most important thing to remember though this, however, is that a flahslight perceived to have "good throw" may not be as useful as a flashlight with "poor throw." While "throwiness" may depend on beam angle and percentage of total light output that goes into that angle, "throwiness" is most certainly not a synonym of "usefulness."

 

[the_guy_with_no_name]

Re: The Real Reason for Throw-an in depth examination

For some reason when I quote you it comes out all garbled. #1 is correct. Not sure what you mean by #2. The SST90 doesn't seem to out-throw anything. It is just an LED. Do you mean the SR90?

Thank you for the comment,

I'm sorry it comes out garbled for you (I am not encrypting my posts. I swear.)

I did mean the Luminous SST90, not the Olight SR90.

I did originally contemplate writing as

The SST90 (in a flashlight) seems to easily out-throw emitters (in flashlights)....

however then things get complex as for those less familiar with optic principles we need to clarify that both flashlights would need to be identical in terms of reflector type, lens type, focal point, etc etc etc and even then this would be factually inacurate because we would get into discussion about a thoeritical "point" of light that we attempt to focus etc etc...

IMHO if we add too many variables when explaining/teaching a concept, both the amount of effort required to grasp the concept and the possibility for misunderstanding the concept increase.

In pure optic theory, even a Led without reflector will project/throw its light as far as one with a reflector although the volume of thrown light will be laughable as it has no practical use. You already know that.

Anyway, its your thread/guide so if you think its better to clarify by adding
(in flashlights) or something else, let me know, Im all for clarity and welcome your feedback.

My only advice/request is:
To avoid further ambiguity in this thread, IMHO it would make sense to begin the thread with or add a concise definition for the term "Throw" to the original post.
Without clarity on that definition as used within this thread, we are essentially discussing a moving target, which makes both contribution & understanding more challenging, and may hamper your goal of providing the much needed guide you have begun.

tgwnn

p.s. adding this to avoid confusion.
I do realize you have defined "throw" nicely in post 46, by the above, I mean adding it to the first post/guide would be ideal to improve clarity for those who read it.

 

[the_guy_with_no_name]

Re: The Real Reason for Throw-an in depth examination

We have a winner

Thanks :thumbsup:

tgwnn

 

[gcbryan]

Re: The Real Reason for Throw-an in depth examination

In furtherance to my last post I should add that the reason that the SR90 can out-throw lights with a higher surface brightness is due to the reflector. The outer portion of the reflector is farther away and therefore the resulting beam has less divergence because that part of the reflector "sees" a smaller source.

Can you fully explain the point you are trying to get across here? This is like pulling teeth

Most flashlights have reflectors and they all have "outer portions" so what is so special about the SR90?

 

[jsholli]

Re: The Real Reason for Throw-an in depth examination

This thread seems to have the potential to be a very informative and concentrated reference for emerging and maturing flashaholics...should we let the OP better develop and support his material before flooding the thread with more comments?

 

[jtr1962]

Re: The Real Reason for Throw-an in depth examination

My only suggestion here to make the concepts being discussed clearer to the layperson would be to include pictures illustrating beam divergence when the relative size of the emitter area and the optic changes. Obviously if you have a huge optic then the emitter becomes a closer approximation to a point source, with the resulting beam being more collimated. I may have more thoughts on all this but frankly I need to clear them up in my own head before trying to post them.

 

[LuxLuthor]

Re: The Real Reason for Throw-an in depth examination

So I have come up with a proposal for a definition of throw and I will invite all of CPF to provide guidance in its refinement.

Throw- A concentrated beam of light that reaches or exceeds the lower threshold of human vision to see a distant target with clarity relative to the user and intended target.

Michael, I understand what you are trying to contribute with this thread, and....well....you sure picked a doozy to try and simplify!

In general, I would recommend keeping a discussion/explanation for how well a light throws--open enough beyond LED's to include examples like Ra's Maxablaster and the MaxaBeam which I compared to DEFT in the photos here, and I'm not sure if the term should include Lasers--only because all of these can effectively "paint" a target.

I think the aspect missing in your proposed definition is that Throw seems to be a description of how effectively an originating light is able to project itself through significant (? outside ?) distances to illuminate a target.

I like the points McGizmo raised in his post #61, but if you add how well the user actually sees the target (which includes reflection back), you are into another can of worms where a 250W floody incan light may actually illuminate the target better, but its flood reflects off moisture & particulates--wiping out your night vision and target discrimination.

In my own mind, I think the most accurate measure of throw is only valid with up close evaluation of the illuminated target in the distance.

I have long thought that demonstrating real world throw, the camera & light meter should be positioned just short of the far (intended target) distance when taking photos, and measurements of the illuminated targets.

I would have liked to have seen what my camera would have captured with the tripod at 800 feet pointing at the trees at 865 feet in those DEFT/Aspheric/MaxaBeam review photos.

 

[easilyled]

Re: The Real Reason for Throw-an in depth examination

My only suggestion here to make the concepts being discussed clearer to the layperson would be to include pictures illustrating beam divergence when the relative size of the emitter area and the optic changes. Obviously if you have a huge optic then the emitter becomes a closer approximation to a point source, with the resulting beam being more collimated. I may have more thoughts on all this but frankly I need to clear them up in my own head before trying to post them.

+1. jtr1962 just beat me to it.

Nothing would explain the concept better than some diagrams with lines representing rays of light being bounced off the reflector with different emitter types and different reflector types.

These diagrams could be as follows:-

1) An SST-90 in a very large reflector shaped like the one in the Olight-SR90-Intimidator.

2) An SST-90 in a much smaller reflector like that of a P60.

3) An XRE in the Olight SR-90 reflector

4) An XRE in a P60 sized reflector.

I realize that these may be difficult to produce in the correct scale and correct geometry of the reflecting rays, but there will be no better way of helping the message come across and it will avoid any ambiguity.

 

[saabluster]

Re: The Real Reason for Throw-an in depth examination

Guys I just want to assure you that this thread will be fully featured with pictures and illustrations. There is a ton more info coming as quickly as I can get this info out of my ADHD brain. Keep in mind that this is a massive undertaking and I have a job, a son that needs to be played with and a wife that needs love. It will all come in due time. I will make a very condensed version of all of this information and put it at the very top of the main post as has been suggested.


I'd like to thank those who honored my request to look and learn. I know it is frustrating but I felt it needed to be done to keep from having a messy thread if you know what I mean. I also need to spend my time writing the information not constantly replying to a bunch of misguided reasoning. That said it seems an impossible task to hold everyone back. Everyone should now consider this thread open to all. That includes Koti. I would caution though Koti that you be a little bit more understanding of how long it takes for me to put a thread like this together and avoid the intense "your so wrong" kind of statements. You have some fine examples from some of the "heavyweights" here in this thread of the right way to disagree.


Since time is of the essence for me right now don't expect me to be able to respond in whole or in part to the posts made in this thread. You guys can duke it out but my responsibility is to get the main post together. I will be observing the posts and if I see something that is suggested as a change and I feel I am in error I will make the adjustments. Just don't expect me to spar with you in the thread right now. As I write new material it will be added to the main post and I will also put it in a fresh post so everyone knows when and what material has been added.


And on that note.



Distance as it relates to reflectors
The beam from a reflector consists of an infinite amount of images of the source laid one over the other. Imagine for a second we were only dealing with one teeny tiny spot on that reflector-say the middle. The beam that is projected will be an image of the emitter albeit very dim. Now move to a spot directly to the side(not closer or farther to the emitter). The same thing happens here. Light from points all across the emitter shine at that tiny spot on the reflector and the beam sent out will be another image. However since you have moved to the side, essentially circling the emitter it(LED's image) will be rotated slightly from the other one. You can repeat this infinitely going around the reflector so that you have image over image over image. This repeated overlapping eventually creates a circle instead of a single image as you would have with an optic.
Now while the basics of what I just described do not change when you move closer or farther to the emitter one thing does change. The size of image that teeny tiny spot projects. The closer that tiny spot is to the emitter the larger the emitter appears just as someone far away appears tiny to you even though your brain knows otherwise. So that tiny spot close in throws an image of the emitter but larger than when we were in the middle of the reflector. And the opposite is true when we move to the outer rim of the reflector. From this vantage point the emitter looks much smaller. Therefore the image thrown is much smaller. Now remember that this whole process is just laying image over image.


So you want to know what part of the projected beam consists of what images? Let's start in the center of the projected beam or the beam you would see on a white wall at 20 feet or so(beam has to have space to mature). The most intense round spot you see is mostly what has been reflected by the outer area of the reflector. It also consists of the less intense and larger images created by the lower portions of the reflector. So all of the reflector contributes to the center of the projected beam but the outer portions of the reflector do not add any intensity to the outer areas of the projected beam.


So to recap. The images from the outer portions of the reflector are the smallest. As we move closer the images get larger.

 

[AEHaas]

Re: The Real Reason for Throw-an in depth examination

90lux of course. It would not however look to your eye as nine times better.

Then it seems as though a 9mm square source giving off 200 lumens/mm could, in theory, give a 9 times higher Lux reading than a 1mm square source giving off 200 lumens/mm (100 feet away)? It would then be able to illuminate a more distant object.

Also, it seems that a 200 lumen point source in a perfect 50cm diameter reflector would give a higher Lux reading at 100 feet than the same source in a 5cm perfect reflector.

aehaas

 

[saabluster]

Re: The Real Reason for Throw-an in depth examination

Then it seems as though a 9mm square source giving off 200 lumens/mm could, in theory, give a 9 times higher Lux reading than a 1mm square source giving off 200 lumens/mm (100 feet away)? It would then be able to illuminate a more distant object.

This is the misguided reasoning I spoke of. Those 8 extra squares are placed to the sides of the center one and therefore do not add to the intensity of the center one only width.

 

[Th232]

Re: The Real Reason for Throw-an in depth examination

Then it seems as though a 9mm square source giving off 200 lumens/mm could, in theory, give a 9 times higher Lux reading than a 1mm square source giving off 200 lumens/mm (100 feet away)? It would then be able to illuminate a more distant object.

Note that the lux reading is at a point, and thus the points next to it don't contribute.

A comparison would be like pressure, pressure = force/area, 9 Newtons over a 3x3 metre area will give the same pressure as 1 Newton over a 1x1 metre area, even though the force in the former example is 9 times that of the force in the latter.

 

[gcbryan]

Re: The Real Reason for Throw-an in depth examination

Is the logic of the smaller more intense images at the edge of the reflector that when you are further away you are "seeing" the entire smaller emitter as opposed to when you are at the center you are closer to the emitter, it appears larger and you are only "seeing" a portion of the emitter?

I know you are right and I'm just trying to picture why this is so.

 

[DM51]

Re: The Real Reason for Throw-an in depth examination

First of all, does the OP of a thread have the authority to decide who gets to post in the thread? This begs the question: who is the owner of a thread; the original poster, the community as a whole, or the person *cough* Greta *cough* paying for the server and bandwidth?
A good topic for another thread, I think.

That is an EXCELLENT question and would make a good topic for a thread in the Cafe.

It highlights why I had some trouble deciding what to do earlier, concerning koti's interventions. I was very much in two minds about whether or not it was right to ask him to refrain from further participation in the thread, and I am not sure I was right to do so.

Everyone should now consider this thread open to all. That includes Koti.

I am delighted you have said this. I hope members will now respond appropriately.

 

[easilyled]

Re: The Real Reason for Throw-an in depth examination

Is the logic of the smaller more intense images at the edge of the reflector that when you are further away you are "seeing" the entire smaller emitter as opposed to when you are at the center you are closer to the emitter, it appears larger and you are only "seeing" a portion of the emitter?

I know you are right and I'm just trying to picture why this is so.

Take 2 converging rays of light from either side of the die. Then trace them to a near part of the reflector.

Do the same to a distant part. The rays have to converge much more to a distant part, therefore the image that more distant part is "seeing" is smaller.

Likewise when you trace the 2 rays reflected out, the 2 reflected rays at the nearer point in the reflector are more widely apart than the 2 reflected rays at the more distant point in the reflector.

Therefore the nearer point in the reflector projects a more diffuse and less intense image.

 

[jankj]

Re: The Real Reason for Throw-an in depth examination

Thanks for putting this together, Saabluster lovecpf

Distance as it relates to reflectors
The beam from a reflector consists of ...

I understand perfectly well that you are speaking of a parabolic reflector. But can you take that assumption for granted? You may consider having a paragraph explaining that you are dealing with a parabolic reflector and what that is. Or maybe this is will be evident from context when the whole piece is strung together - or from illustrations.

I have a pretty good idea of what you're struggling with - explaining stuff such as this in a concise and precise way without too many words is though. I must say it is looking very promising, and I look forward to follow your progress