The Real Reason for Throw - an in depth examination

[AEHaas]

"a collimated light source's intensity doesn't fall off with the square of distance ( the extreme example of a perfectly collimated light source has the same intensity regardless of distance )"

A photon of light travels forever until it hits something. It is only that enough are concentrated such that more reach the target of desired illumination.

aehaas

 

[saabluster]

"a collimated light source's intensity doesn't fall off with the square of distance ( the extreme example of a perfectly collimated light source has the same intensity regardless of distance )"

A photon of light travels forever until it hits something. It is only that enough are concentrated such that more reach the target of desired illumination.

aehaas

Who are you quoting from? You have quote marks around that sentence.

Edit: Finally found it. The quote button is there for a reason.

 

[dymonite69]

That only applies to an uncollimated light source. A collimated light source doesn't follow the inverse square law.

But the light reflected back from the target is not collimated so the irradiance will decrease with distance.

 

[copperfox]

The sun is completely omnidirectional and I would prefer that illumination and range over any flashlight you can throw against it (pun intended)

That is exactly my point, exactly! Nobody would say the sun out-throws something like the a Tiablo. There is more to the subjective term "throw" than simply number of lux on a distant target and the sun is a perfect example. Some lights (and the sun) have a broad distribution and tons of lumens. These lights may even put higher lux on a target than a flashlight with a narrow beam, but that doesn't mean it has better throw, it just means it provides the user with better distant object recognition. Object recognition is NOT the same as throw. If we want to come up with a correct definition, we must look at the extreme and boundary cases, not just the common ones.

 

[dymonite69]

That is exactly my point, exactly! Nobody would say the sun out-throws something like the a Tiablo.

So you consider beam collimation far more important than getting useful illumination onto your target? Give me the sun any time.

We are then back to the low-powered laser example - close to ideal collimation but no oomph to light up anything except a coin and no breadth to define the object.

 

[JaguarDave-in-Oz]

but that doesn't mean it has better throw, it just means it provides the user with better distant object recognition.

So I have just learned that I am no longer interested in torches that throw. Now I'm only interested in torches that display a measure of a "distant object recognition" ability which was the only reason I thought I was ever interested in throw in the first place. Back to square one for me. I'm now going to concentrate on practical "distant object recognition" than theoretical "throw".

 

[McGizmo]

...Nobody would say the sun out-throws something like the a Tiablo. ...

I would! Let's pick the moon for a target. I can provide you a beam shot of the sun illuminating the moon and you give me one of a Tiablo illuminating the moon or any portion of it. :nana:

Saabluster states:

..You can have a highly collimated beam but no intensity and therefore no real throw.

Following this logic then you can have an uncollimated beam with significant intensity (sun) that does therefore have some throw.


But, I think inherent in your objection is the presumption that we are talking about a portable and likely hand held light source with which the source as well as the viewer are in close proximity with the need to effectively illuminate a target at a significan distance from the user and his (her) light source. The sun therefore would be disqualified.

For everyone who needs or wants an idea of what throw is and even some means of comparing the throw of dissimilar lights, I hope the OP and this thread can lead you to some good answers.

 

[saabluster]

I would! Let's pick the moon for a target. I can provide you a beam shot of the sun illuminating the moon and you give me one of a Tiablo illuminating the moon or any portion of it. :nana:

Yes I would have to agree that the sun would out throw the Tiablo but just barely.

Saabluster states:

Following this logic then you can have an uncollimated beam with significant intensity (sun) that does therefore have some throw.


But, I think inherent in your objection is the presumption that we are talking about a portable and likely hand held light source with which the source as well as the viewer are in close proximity with the need to effectively illuminate a target at a significan distance from the user and his (her) light source. The sun therefore would be disqualified.

For everyone who needs or wants an idea of what throw is and even some means of comparing the throw of dissimilar lights, I hope the OP and this thread can lead you to some good answers.

You are correct that the definition I provided is in context of flashlights as it should be right? A quick look in the dictionary will show that definitions given in a particular context are not unusual. Since we are in that context the sun is right out along with the lasers but for more reasons than just the context and a little bit of applied "common" sense. The definition says "concentrated" and "beam" which indicate a form of collimation is being used. So the sun is out.

This does however bring up a good point. What about a really really bright light source without any form of collimation? Again reason must rule the day as well as common usage. Just about anyone with any knowledge on this site would call an uncollimized light source a flood light. Also the amount of light necessary from a true flood source to see something off in the distance would be extraordinarily high. This means that more than likely this device could not be classified as a flashlight due to the size that would be required for the necessary power source.

 

[gcbryan]

If this discussion is supposed to be practical (which it seems is less and less likely to me) then a better post would be one where one describes why the DEFT throws so well.

As in it starts with the emitter...the surface brightness of the XR-E is greater than the other emitters available. Then it has to do with at what level it's driven. The next variable is the optic or reflector...this type of reflector doesn't work but this one does (or optic) and here's why.

Here are the other variables and why I chose this one over that one. That's practical. If one understands why the DEFT throws better than another light then the factors involved will be obvious.

If one understands how to mentally construct such a light then one would better understand how to pick a future light...again that's practical.

That way we don't need to talk about lasers or the sun or argue over definitions.

It seems no one can in one or two paragraphs and in laymens terms explain this so why not just describe how one builds such a light and what choices one has to make at each step with the components?

 

[saabluster]

If this discussion is supposed to be practical (which it seems is less and less likely to me) then a better post would be one where one describes why the DEFT throws so well.

As in it starts with the emitter...the surface brightness of the XR-E is greater than the other emitters available. Then it has to do with at what level it's driven. The next variable is the optic or reflector...this type of reflector doesn't work but this one does (or optic) and here's why.

Here are the other variables and why I chose this one over that one. That's practical. If one understands why the DEFT throws better than another light then the factors involved will be obvious.

If one understands how to mentally construct such a light then one would better understand how to pick a future light...again that's practical.

That way we don't need to talk about lasers or the sun or argue over definitions.

It seems no one can in one or two paragraphs and in laymens terms explain this so why not just describe how one builds such a light and what choices one has to make at each step with the components?

Well that is the main point of this thread. I can tell you why the DEFT throws so well but I have no intention of that being the focus of this thread. Here you go.

It throws so well because it uses the LED with the highest surface brightness combined with a very efficient optical system(throughput) where the main refractive surfaces are relatively far away from the source thereby providing good collimization. That's it. That's the reason.

The problem is people want and need to know more than just the basic reasons. They need to know what the significance of the distance is or the significance of the surface brightness is.

I would also add that instead of examining the DEFT and drawing conclusions on other flashlights based on that it is far better to know the basics behind any flashlight. Then it will be obvious why the DEFT throws like it does.

 

[saabluster]

It seems no one can in one or two paragraphs and in laymens terms explain this so why not just describe how one builds such a light and what choices one has to make at each step with the components?

By the way that was only one sentence.:nana:

 

[copperfox]

So you consider beam collimation far more important than getting useful illumination onto your target? Give me the sun any time.

We are then back to the low-powered laser example - close to ideal collimation but no oomph to light up anything except a coin and no breadth to define the object.

No, I didn't assign importance to one or the other. As I said back on page 3: "throwiness" is most certainly not a synonym of "usefulness."

The point I'm making is that you can have a very bright flood light put more light on a target than a light with a tight beam. But McGizmo is right in that the sun is not a totally practical example when we are accustomed to being limited by brightness in our handheld devices, so for most of our experience we have either low lux, floody light, or high lux concentrated light. I'm saying the beam pattern and the lux on a target are not mutually exclusive. With something as brutally powerful as the sun, sheer lumens can easily compensate for the lack of a narrow beam.

The quality of distant field illumination is certainly a function of overall brightness (the sun is hugely bright, but emits light in all directions), but it's not the only factor. This is why I came to the conclusion that beam pattern is not the only factor when considering throw; percentage of total output in that collimated beam is also a factor.

Even with a good definition of throw, it is still going to be subjective. Who is to say that a 200 lumen, 8 degree beam is more or less throwy than a 160 lumen 6 degree beam?

 

[dymonite69]

I wanted to illuminate the boundary fence of a 5 acre property, a car at 150m or the length of my 80 m driveway. I considered the Dereelight DBS or Tiablo TK40 +/- aspheric. In the end I chose a 35W HID. Which is throwier? Which lights up further?

 

[gcbryan]

By the way that was only one sentence.:nana:

Now, that wasn't so hard was it?

...and the SR90 throws so well because it has a large diameter reflector...is that correct.?

Now we're getting someplace

 

[gcbryan]

No, I didn't assign importance to one or the other. As I said back on page 3: "throwiness" is most certainly not a synonym of "usefulness."

The point I'm making is that you can have a very bright flood light put more light on a target than a light with a tight beam. But McGizmo is right in that the sun is not a totally practical example when we are accustomed to being limited by brightness in our handheld devices, so for most of our experience we have either low lux, floody light, or high lux concentrated light. I'm saying the beam pattern and the lux on a target are not mutually exclusive. With something as brutally powerful as the sun, sheer lumens can easily compensate for the lack of a narrow beam.

The quality of distant field illumination is certainly a function of overall brightness (the sun is hugely bright, but emits light in all directions), but it's not the only factor. This is why I came to the conclusion that beam pattern is not the only factor when considering throw; percentage of total output in that collimated beam is also a factor.

Even with a good definition of throw, it is still going to be subjective. Who is to say that a 200 lumen, 8 degree beam is more or less throwy than a 160 lumen 6 degree beam?

You're getting off track when you are talking about a narrow beam. The sun can "throw" light to the earth (is it reflected back to the sun in such a way that an observer could see it...I don't know) so it has nothing to do with wide vs narrow beam. For beam to matter with the sun you'd have to go further than the earth. You'd have to go far enough to where the wide beam of the sun didn't illuminate the object and then you would have to narrow the suns beam and see how much further it would throw.

The point is is that throw is not about the narrowness of a beam. It's about enough lux on the target for you to see it. You can illuminate a barn across the street with a flood light or a spot light. It's not the lumens overpowering anything...it's still about lux on target.

The only reason a narrow beam comes into play is that if you keep the output constant then a narrow beam will put more lux on target than a wide beam. At some intermediate range it doesn't matter as they will both illuminate it.

 

[saabluster]

Now, that wasn't so hard was it?

...and the SR90 throws so well because it has a large diameter reflector...is that correct.?

Now we're getting someplace

No the SR90 throws so well because it has reflective surfaces relatively far from the source while still having a good capture angle and relatively high surface brightness.

Wow! That was also one sentence. What's happened to me?!

 

[gcbryan]

No the SR90 throws so well because it has reflective surfaces relatively far from the source while still having a good capture angle and relatively high surface brightness.

Wow! That was also one sentence. What's happened to me?!

You just need a good director!

So, what would you call this particular type of reflector...a larger diameter but smooth as well as deep reflector?

 

[saabluster]

Well the tgwnn is helping me with some visualization guides to help everyone. So a massive thanks goes out to him.

I also need some help from some of our resident geniuses that loves all that math.(not me) Maybe IMSabbel?:shrug: I need some help on figuring out the amounts of light gathered based on the spatial distribution of different light sources in different collimators. I know intuitively how all this stuff works but when it comes to the math involved I throw up my hands. Anybody want to help me out with this one?

After we get this all together I will put all the contributors in the main post. This is a larger task than I really thought it would be so any help I can get will get this done faster and frankly better. Thanks.

 

[wapkil]

You're getting off track when you are talking about a narrow beam. The sun can "throw" light to the earth (is it reflected back to the sun in such a way that an observer could see it...I don't know)

It is reflected but the ambient light level at the Sun may make it a bit hard to see. I think though that if the observer is comfortable with what they consider the room temperature there, the illumination shouldn't also be a problem

As far as I know the stars other than the Sun are usually treated like the collimated light sources - they are far enough to be seen as the point sources. It shows once again that frequently what is important is not the properties of the light source but the observable effects. It's philosophical but I would say that the Sun throws much better than any flashlight - just because it illuminates objects farther away. I don't see why the source that throws well in all the directions shouldn't be said to have a large throw distance.

 

[LuxLuthor]

My first response since I last posted is to just smile. Here are my thoughts, in no specific order.

1) Michael, quit responding to every post! LOL! I went down 20 side tunnels just since my last post. I should send you some of this Ethiopian Sidasso roasted coffee to get back to the important stuff!

2) I just want to be clear that I did not mention the NEMA 0.25 Lux figure, and can neither confirm or deny any such item. :green:

3) I do think it is useful for CPF as a community to recognize the stature of NEMA specifically, and established standards generally--as a priori while in the process making up and defining a new term such as "throw." Said another way, IMHO, existing standards established by official bodies should subsume anything we come up with. We cannot pretend that we have any more validity than a group of nut-job hobbyists. (I say that with great affection).

4) Michael, I do see the OP as now making it clear that you are including multiple light sources. Thank you.

5) I don't think those of us who bring up Lux and/or Distances are "hung up on it" as a measurement of throw as Copperfox suggested. Rather we are thinking towards objectification, as one man's lower threshold of human vision to see a distant target with clarity, is another man's need for corrective lenses.

6) As if to illustrate my previous point, after reading the "ask the wife" experiment, earlier tonight while commiserating with my neighbors over our recent 2 day power outage, they again wanted to see my 'big lights' from the night before. I brought out the Barnburner spotlight, a DEFT, and Mag85. After they played around with them like three kids discovering their "inner flashlight geek" that I suspects lies dormant in all of us until having a 'CPF epiphany,' I asked three of the guys:

"Which light would they say threw the furthest?"
​

They all looked at me like I had 4 eyes, each responding in turn:

"What?"
​

"What do ya mean 'threw the furthest?'"
​

"I dunno."
​

I expanded by asking:

"Which light allowed them to best see the street sign down there [about a block away]?"
​

They all responded:

"That one! [the Barnburner]"
​

I'll let the group draw their own conclusions.

7) McGizmo, the NEMA standard does not address what I will summarize from your post as the "cone of illumination," but what is described in the pattern of a steradian. There are many other things I wished they addressed, but alas, here we sit.