Re: The Real Reason for Throw-an in depth examination
I take the term throw to be based on a measure of lux taken from a light source, beyond any point of beam conversion; that is, reasonably down stream, where the beam is diverging. In comparing two beams of light from two flashlights, the one with a higher measure of lux at the same (reasonable) distance would be considered the light with greater throw. Is this in agreement with your definition of throw? I don't want to make any false assumptions here and since you are going to provide us with the real reason for throw, it would be great if we are all on the same page as to what "throw" is.
I should make something very clear at this point. I don't care one iota about theory that has no effect on the world we live in. To ponder on such things is a massive waste of time in my opinion. I care about things that cause real discernible effects in my life. The "other" thread has a lot of good information but its bent towards things that can't happen leaves me feeling a bit short of satisfied. I appreciated your efforts to get them to focus on the topic from an angle that would help people see the practical application of the study of light as it relates to flashlights. We are here on CPF to discus flashlights. Flashlights have a clear purpose-to help people see. That is practical or useful.
In creating a definition for throw we run into problems that are relative to the conditions. First I would make the proposal that our definition of throw be informed by the colloquial use of the term here on CPF. As has been mentioned before on this site in the most literal sense of the word every light has equal throw in that the light from all flashlights will travel infinitely unless acted upon. That said that is not how we use the term. When people talk about throw the implication is how far you can see. Since a flashlight's "job" is to allow us to
see targets the defining factor must be target
recognition not that one could see faintly that light was reaching the target. This makes a defintion of throw very difficult (but not impossible) since there is no clear cut measure of what would be considered intense enough to reach that threshold of target recognition due to the many factors at play such as the user, ambient light, weather conditions, target shape and color and so on. I see this task as similar to trying to come up with a definition for such words as "good". Good is a relative term and yet you will find a definition for it in the dictionary.
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.
Lets use this in some sentences we see fairly often here on CPF.
"How far does that flashlight throw?"
In this context the person wants to know the farthest or outer limit of the flashlight while still meeting the minimum definition of 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.
"Will this flashlight throw that far?"
Here the person has a set distance in mind and want to know if it reaches
or exceeds the lower threshold of human vision to see a distant target with clarity relative to the user and intended target.
"What is the farthest throwing light?"
This is perhaps the easiest one to answer because the light with the highest measured lux will always provide the most throw even if we can't put a specific distance measurement on that throw.
Two compare the "throw" of two different lights, I would think that actual measurements would be the most reasonable basis of comparison and again, I would look to a measure of lux (or similar unit of measure) to establish such a comparison.
Yes measurements of lux does help the CPF populace to quantify the relative performance of lights. It would be hard however to take a specific lux measurement and declare that as the point where it meets the definition of throw as mentioned above since throw is a relative term. We could do some extensive experiments to try to nail down what lux in what ambient light conditions would provide the average person usable visibility but because of the relative nature of throw a measurement cannot be used to define throw.
Hypothetically, consider an elephant at 50' of distance from you and your flashlights. You have two flashlights. Both emit 100 lumens out the front end. One has a super tight collimated beam that gives you a circle of 2' in diameter at 50' and the other has a much larger beam angle and gives you a circle of 50' in diameter at 50' of distance. With the tight beam light, you see a nice bright gray 2' diameter circle of something 50' away. This light definitely out throws the other. With the other light, you see the whole elephant but not with the same surface intensity of reflection as with the tight beam. You have enough "throw" to identify the object as an elephant and the reflection in his two eyes lets you know he is staring straight at you. In both cases, the lights allowed us to see the elephant with our own eyes but perhaps identifying the elephant was easier with the light that didn't have the longest or greatest throw. Provided sufficient lux is present at a distant object, we can see it. In your terms, provided a light has sufficient throw, it is suitable for illuminating such a distant object, yes?
In this case both lights meet the minimum definition for throw at
that distance. Obviously some reasonableness needs to be introduced in this area. This definition is for flashlights not lasers or baseballs for that matter. A
flashlight can be moved about to ascertain what the target is even if the beam is narrow as long as the intensity is sufficient to allow recognition of the target surfaces. If we were to exclude this light from the definition of throw what would be the case when we increased the distance and now the wider beam light provides no recognition of the elephant due to low lux but the narrower beam light fully lights up the elephant with full recognition? Since the entire purpose of defining throw is about distance we cannot make exclusions based on the nearness of an object no?
Your thread title stating The Real Reason for Throw is a bit confusing at this point but perhaps it will become clearer as you move along. Will you be comparing real VS false or imagined reasons for throw? By Real Reason do you mean to get into the justification or need for throw? That is to say why we may want or need throw? Or is it as it seems, at this point, that you will be explaining how one develops throw by virtue of the use of secondary optics as well as the nature of the light source itself and how it lends itself to management by optics?
The reason for that title is because so many people here believe lumens are what create throw. Obviously with no lumens you have no throw but you cannot make the assumption that the SST90 will out-throw the XR-E because of the immense output of the SST90. Yet that is what people here are doing. People need to know the real reason for throw. Why do they need to know? Besides the fact that it is always better to know the truth they may buy one light over another based solely on the fact that one has more lumens than another when what they really need is the farther throwing light.
My questions are rhetorical but perhaps worthy of consideration if they haven't already been anticipated and planned to be addressed in your future installments. No need for any direct response or further side tracking.
If this post is an unnecessary distraction, feel free to ignore it completely. No worries.
McGizmo you do not speak off the cuff and I know you have put considerable time into learning the science behind flashlights. Your input is always welcome.:thumbsup: I wish more people would follow your example of contemplation before posting.
Even if you had a point light source and perfect optics, the beam would still diverge due to diffraction. This is an inescapable consequence of the wave nature of light.
http://en.wikipedia.org/wiki/Gaussian_beam#Beam_divergence
For a flashlight, the non-point nature of the emitter will be the dominant reason for beam divergence. But for lasers, diffraction is the main reason. The only way to reduce (but not eliminate) this effect is to use a shorter wavelength of light or else start with a wider beam.
This highlights the difficulty I face in trying to put a thread like this together. This thread is intended to help the layperson and as such does not get into all the various intricacies involved that frankly don't amount to a hill of beans. My point is to not focus on such things as a Gaussian beam as it has no relevance to what we do as the distances are such you will never see the effects. Such things must be left unsaid lest we make the explanation too complicated for the layperson to follow and they give up. I don't want to go there. Thank you for trying to make sure the t's are crossed though.
I have been contemplating this entire thread topic for the better part of two years now. Anyway I thank those of you who have restrained yourselves. I know it is not easy. Thank you.
