The Real Reason for Throw - an in depth examination

[McGizmo]

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

The reflective nature of the object of interest is not always the same and this too comes into play. Reflective street signs can light up at hundreds of yards being illuminated by a weak flood source that can't reveal a skunk at 50'.

It seems that the idea of throw if not its definition has been well fleshed out here by the group of contributors. The OP's concern that folks equate the measure of lumens to a lights ability to "throw" will continue to be a source of confusion for anyone not understanding the various measures of light output or more specifically, the difference between lux and flux.

If there were an instrument like a spotter's scope that were to measure the return light from a distant object, this might well be the tool to use to measure effective throw. A lux meter placed behind a scope as it were.

One could place a lux meter on a standardized target and then back away from this target while illuminating it until the threshold was reached for the individual at which point they felt they could no longer discern the target. The measure of lux (now measured at the target) at this distance could then be established for the individual as being the minimum for this specific target. They could then repeat the process with other light sources and get a feel for the various throws of these lights. It would also be illuminating to see how and if the minimum lux necessary for this target were to vary because of the spectral nature of the light source itself.

I am still confused by the actual title of this thread. I would submit that the real reason for throw is simply that there are times when a person needs to be able to effectively illuminate a distant target and for that purpose needs a light that can provide adequate throw.

Clearly different lights will have various abilities to throw light and illuminate targets at any distance. Their success is so subjective in nature and dependent on both the observer as well as the nature of the target that it is unrealistic to hope for some simple and objective measure of throw.

 

[jtr1962]

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

The theoretical perfectly collimated source would still lose lux over distance in the real world because of moisture, dust, pollen, and other matter in the air to absorb or diffuse the light. Unless you were talking about a theoretical environment as well.

Of course it would, and also the target's albedo ( i.e. reflective ability ) would come into play as Don mentions. I'm just looking for some standard where a light can be considered to "throw" x meters if it puts a certain amount of lux on a perfectly reflective target in perfectly clear air at that distance. We can then correct for the target's albedo and any atmospheric factors if we wish. Call what I propose a chart for "theoretical maximum throw". In practice a light which might throw 100 meters according to this standard might only throw half that much under real world conditions. However, all other lights would be similarly affected. The relative throw between different lights would still remain the same.

Right now throw as is commonly used is a little too nebulously defined. It's sort of the same as telling someone to drive at a "safe, comfortable speed". That may well vary by a factor of two or more depending upon the driver. If we settle on the number of lux at any given distance where a person with normal vision can identify a target, then at least we've removed a lot of subjectivity. Now if someone says their light throws 100 meters it's meaningless. They may have very acute low-level vision and not need much light returning from the target. They may be shining it at a very reflective target. On the other hand, for someone like me with 20/200 vision no light made, including the sun, can reasonably allow me to see objects 100 meters away well. Quantifying things when possible makes sense. For example, we sell light bulbs with lumen outputs right on the package. We don't say "dim", "a little less dim", "sort of bright", "bright", "really bright", etc. Those terms would mean different things to different people. I might consider 2000 lumens in an average room dim. Others might consider it very bright. Same with throw.

 

[easilyled]

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

......
I am still confused by the actual title of this thread. I would submit that the real reason for throw is simply that there are times when a person needs to be able to effectively illuminate a distant target and for that purpose needs a light that can provide adequate throw.
..........

I don't think that is the context in which the title of this thread was created, although I agree with you that it is misleading.

If I'm not mistaken saabluster wanted to clear up a lot of misconceptions that people have/had about what constitutes the CPF common parlance term "throw"

Therefore the title is not meant to imply the need for throw but rather the science behind it.

Maybe "An in-depth examination of factors favoring/contributing to long-distance illumination (throw) in flashlight design" would be less confusing.

 

[Benson]

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

I am still confused by the actual title of this thread. I would submit that the real reason for throw is simply that there are times when a person needs to be able to effectively illuminate a distant target and for that purpose needs a light that can provide adequate throw.

Perhaps something like "The real mechanics of throw"?

 

[gcbryan]

How about just "The Mechanics of Throw". The word real seems to be the confusing part for some.

It could be called "Throw is not a Function of Lumens" since I think that was the original point.

It's interesting...we have two makers of fine flashlights. One is a maker of lights that have extreme throw and is the OP. He is probably concerned at least somewhat that people may be buying newer higher output flashlights believing they will out throw his product.

Another whose flashlights are more functional where extreme throw isn't needed is the one more interested in discussing when and why is throw needed in the first place.

I think more info is needed regarding the mechanics of throw than is needed for someone to determine when and why and to what degree throw would be needed. The answer to that one is simply whatever it takes to get the job done.

Most people in most situations don't need extreme throw. However, most of us like it and some do need it and most of the posters in this thread I believe do want to make sure we understand all of the mechanics of throw...if for no other reason than it's an interesting subject.

I think it is good that an attempt has been made to keep the decision to the practical world of flashlights as well.

 

[LuxLuthor]

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.

 

[wapkil]

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 this information. I didn't know that such a standard finally appeared

If I understand correctly, to determine the "beam distance" (i.e. our "throw") they simply measure the maximum illuminance (at 2, 10 or 30 meters) and use the inverse square law to determine at what distance it is 0.25 lux. IMHO sounds much better than trying to define the throw in relation to some "lower threshold of human vision" (IIRC currently believed to be around 500-1000 photons/second EDIT: or maybe an order of magnitude better :thinking:, either way I believe it would be really hard to use it in any definition with a practical meaning).

 

[dymonite69]

The lighting level has to measured at a reasonable minimal distance so that beyond which the beam pattern remains relatively constant. In other words. the illumination pattern of the relative contributions of hotspot, flood and spill should stay in relative proportion from the distance onwards.

Otherwise a manufacturer can 'cheat' the standard by designing the beam's focal point at a particular distance they know it will be tested at but in fact which diverge significantly beyond it.

 

[JaguarDave-in-Oz]

Otherwise a manufacturer can 'cheat' the standard by designing the beam's focal point at a particular distance they know it will be tested at but in fact which diverge significantly beyond it.

That would be nice if they could say have it converge to a point at say 150 yards or whatever distance and then state that distance on the box........

 

[McGizmo]

....
Otherwise a manufacturer can 'cheat' the standard by designing the beam's focal point at a particular distance they know it will be tested at but in fact which diverge significantly beyond it.

I don't think such a design with a convergence in beam down stream like you suggest is trivial nor would I guess any manufacturer would attempt a "cheater" with the purpose of cheating like this. Such a design would actually have some great merit in its own right and especially if the external focal point of convergence could be adjustable!!

If someone needs throw then they need throw. If someone wants throw then they want throw. It's simple. What is not simple is evaluating information and specs provided by a light maker and determining if the need or want for throw is accommodated by the light in question. It would be great if assigning a simple throw number to a light would rank it among others in regards to throw and as far as I know, such a number will have to relate to lux or a similar measure of light intensity at the target's surface and not a measure of light at the flashlight.

 

[kengps]

A "Focal point" 150 Meters down range??? We're talking reflectors here. They focus them for infinity and it spreads out from there. If it were posible to adjust a focal point of a reflector (or lens) then you would be able to bring the spot down to the size of the reflector at the focal point. Ever seen a flashlight that could do that at 150 Meters? It is impossible. the best you're going to get is a focal point of infinity, and it will spread out from that point on. No way to cheat as described.

 

[dymonite69]

But if the testing standard only measured lux at distances at less than 10 meters (like the uncontrolled tests often seen on this forum), then this could easily lead to misleading interpretation of the results.

 

[the_guy_with_no_name]

Many very good points have been made such as differing reflective properties of the target, differing atmospheric and environmental conditions as well as the differences that occur related to visual perception which does indeed differ greatly between people.

So are we any closer to agreeing on what throw is?

I believe a key point is that a consistent definition is used to "measure and rate" throw.

IMHO, Without getting too stuck on the important definition, I do think for the OP can continue the original post even with the "relative" definition (as I observe it) of throw as the main purpose seems to be what influences throw and how to achieve more/less of it and consider coming back to throw again if the OP wants or sees a need to in post #1.

I do also think that it is beneficial to start a new thread with title:
Define Throw (or something similar) so we can thrash this thing out until we have a system/scale to measure and rate throw in a way that is most valuable to the largest number of CPF'ers and the general flashlight user population, and ideally something that even flashlight manufacturers would consider implementing as a way to inform potential buyers as to the throw ability of a flashlight (at least for lights they consider "throwy" - whatever the heck that means).

Appreciate any & all feedback.

tgwnn

 

[saabluster]

I have been very busy and have not had time to respond to all these posts. Its too much for me frankly. My ADD means that I have to read things 3 and 4 times as I forget what I just read by the time I get to the end of a sentence. That means to respond to just one of those big posts from you guys takes me about an hour and a half to two hours. I can't respond to all of you even though I have plenty to say.

I get the feeling people here are not seeing the whole picture and really taking a hard look at the definition I provided and the guidance used to come to its completion. I think that even if God himself came down and gave us the definition there would be no shortage of dissenters here.

Many very good points have been made such as differing reflective properties of the target, differing atmospheric and environmental conditions as well as the differences that occur related to visual perception which does indeed differ greatly between people.

So are we any closer to agreeing on what throw is?

I believe a key point is that a consistent definition is used to "measure and rate" throw.


IMHO, Without getting too stuck on the important definition, I do think for the OP can continue the original post even with the "relative" definition (as I observe it) of throw as the main purpose seems to be what influences throw and how to achieve more/less of it and consider coming back to throw again if the OP wants or sees a need to in post #1.

I do also think that it is beneficial to start a new thread with title:
Define Throw (or something similar) so we can thrash this thing out until we have a system/scale to measure and rate throw in a way that is most valuable to the largest number of CPF'ers and the general flashlight user population, and ideally something that even flashlight manufacturers would consider implementing as a way to inform potential buyers as to the throw ability of a flashlight (at least for lights they consider "throwy" - whatever the heck that means).

Appreciate any & all feedback.

tgwnn

I see no need for an entire thread just for the definition of throw as we already have a definition both in this thread and in industry papers. The document Lux pointed to has everything spelled out so there would be no benefit to the industry by providing any guidance from us on the quantifying of throw. I have that document and I think what they have done is excellent. Very simple and easy to do. They did a good job on it. That publication understandably focuses on the quantifying of various points of performance so that any claims to the consumer are clear and consistent brand to brand. Therefore they were not interested in a definition of throw that describes the word's use in the wild-here on CPF. They need hard numbers for a standards document. If that is all anyone here wants then the work is already done.

I submit however that beyond the word being used in the sense of just raw numbers people use use the term in a more general sense. I also submit that the definition as provided by them(ihs/global) is incomplete precisely because it does not deal with all the factors that can affect the visiblity in the the real world(the subnote they provide is an assumption of perfect weather but does not deal with such things as ambient light). Following their guidance on throw does not mean you will be able to see anything at the point a light meets their criteria. I have said it before and I'll say it again. What is the point of a flashlight? Why do they exist? If you can't see the target can you say that that flashlight can throw that far(even if it does meet the official criteria).

This is where you guys will just have to let something go. My definition provides for all the possible circumstances that could have any bearing on throw while highlighting the main(entire?) points such as..can the user see the target?.

People here want a definition that shows what lux at what distance in what conditions with what kind of beam and what light source with the difference between standing behind the beam vs the side and the albedo of the target vs the color contrasts of the target and background and so on and so forth. People!:hairpull:

What you guys want is a chart or a pretty graph with numbers. That is not a definition. It helps to "define" what throw is in a certain circumstance but it does not define throw.

FYI tgwnn don't take my frustration as being aimed at you just because I quoted your post here. I just picked one and went with it. I appreciate your contribution here.

Time to go play with my son at the park.:kiss:

 

[DM51]

I don't see any need for you to respond to every post here, and I'm sure other members will understand if you don't answer every single point. You've already recognised that members will want to express their own views on this very interesting topic, and they are going to do so anyway, lol.

I don't think it is necessary to open a separate thread at this stage. This one is doing fine. It's one of the best threads we've had for a while – you may not think so, but it is. There's a lot of excellent input, and it has generated a great deal of interest.

You could concentrate on completing your thesis in post #1. You don't need to try to deal with the avalanche of input here. It would be like trying to nail Jello to a wall, or eat soup with a fork while the soup is still being poured on to your plate. mmm soup…

some square root algebra

mmm square root… drooooll… doesn't roll off the plate like beetroot and make purple marks on your pants …

OK sorry, back on topic, lol

 

[jabe1]

I find myself scheduling time during my day to read-up on this post.
Excellent read.:twothumbs

 

[saabluster]

I don't see any need for you to respond to every post here, and I'm sure other members will understand if you don't answer every single point. You've already recognised that members will want to express their own views on this very interesting topic, and they are going to do so anyway, lol.

I don't think it is necessary to open a separate thread at this stage. This one is doing fine. It's one of the best threads we've had for a while – you may not think so, but it is. There's a lot of excellent input, and it has generated a great deal of interest.

You could concentrate on completing your thesis in post #1. You don't need to try to deal with the avalanche of input here. It would be like trying to nail Jello to a wall, or eat soup with a fork while the soup is still being poured on to your plate. mmm soup…

mmm square root… drooooll… doesn't roll off the plate like beetroot and make purple marks on your pants …

OK sorry, back on topic, lol

Thanks. I just get the feeling I am offending people if I don't respond to them. Hopefully everyone can understand.

Well I looked back over my main post and decided Lux was right about it seeming to be too LED centric. It was not intended to be that way but it was nonetheless. I have added some information and tweaked stuff here and there in the hopes that it is clear I intend this to be for all the major light sources not just LED. Let me know if I did enough to remedy that. Thanks.

 

[dymonite69]

I get the feeling people here are not seeing the whole picture and really taking a hard look at the definition I provided

I see no need for an entire thread just for the definition of throw as we already have a definition both in this thread and in industry papers.

For the sake of clarity, this was your original definition.

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.

My definition provides for all the possible circumstances that could have any bearing on throw while highlighting the main(entire?) points such as..can the user see the target?.

What you guys want is a chart or a pretty graph with numbers. That is not a definition. It helps to "define" what throw is in a certain circumstance but it does not define throw.

Do you want a definition that enables one to objectively predict the capabilities of a flashlight in the field or do you just want a philosophical concept that has no practical value?

 

[mudman cj]

But if the testing standard only measured lux at distances at less than 10 meters (like the uncontrolled tests often seen on this forum), then this could easily lead to misleading interpretation of the results.

Agreed. I would like to add that it is possible to check one's measurements for conformance to the inverse square law. If the measurements deviate from the law then they were not taken at great enough distances from the light source. This is more of an issue with light sources having large reflectors such as most HID lights, lanterns, and of course spotlights. Posting lux readings without taking measurements at many distances and confirming a fit to the inverse square law is misleading.

Thanks to Lux and wapkil for bringing up the new standard. That figure of distance at which a target is illuminated with 0.25 lux is exactly the kind of adjustment to the old CPF standard of distance for 1 lux that I have been wanting. Using the 0.25 lux standard should bring measurements more in line with real world use and also with throw values reported by manufacturers.

Of course, we must keep in mind that manufacturers use their own methods to determine throw as do individual members. Variation in equipment and methods will result in variation in results.

 

[the_guy_with_no_name]

FYI tgwnn don't take my frustration as being aimed at you just because I quoted your post here. I just picked one and went with it. I appreciate your contribution here.

No offense taken at all :twothumbs


I too thought that things were getting bogged down somewhat in the definition.

I see no need for an entire thread just for the definition of throw as we already have a definition both in this thread and in industry papers.

No need to re-invent the wheel unless it can be improved on.
I just wondered if the rating method that Lux Luthor brought too attention was well enough suited to clarify throw in the sense of how its typicaly used on CPF.

Also, I don't think you need to reply to every single post, jeez that will take forever.

Use what is useful to you and pass over what isn't (especially goes for my long rantings )

Other than maybe working on some images as we discussed, I think I'll take time off posting in this thread to allow you fair time to add to the guide more efficiently.

Thanks to everyone who contributed so far for a great thread.

tgwnn