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Thread: Optic theory

  1. #241
    Flashaholic* Ra's Avatar
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    Wink2 Re: Optic theory

    Hi koti,

    Thanks for your remark..

    It shure was fun to do. And if you have questions about this subject, don't hessitate to ask!
    That is what these forums are about! To shine light on what others want to know..

    all the best,

    Ra.
    The proof of the existence of intelligent extra terrestrial life lies in the fact that they didn't contact us yet...
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  2. #242
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    Default Re: Optic theory

    Actualy I do have a question about the "optics" subject...
    Can You get me an EF 70-200 f/2.8 L IS in that lab of yours for free for being a good sport ?
    I'll take a used one too...

    cheers

    Edit:
    Just kidding Ra...thank you again for all your input in this thread, I learnt a lot.
    As for surface brightness (I actualy got realy atracted to the term after reading your posts) which you mention a lot in your posts, I have a toy that should be able to beat Your Maxablaster
    Here it is...a 372mw (measured) green laser...full angle divergence = <0.9mrad
    Runs on a single 18650 (2500mah lasts for 3 to 4 minutes max)


    As for "throw" and surface brightness I should own all the participants of this thread
    Unless that is...someone here has a true 400mw+ TEM00 green laser





    Quote Originally Posted by Ra View Post
    Hi koti,

    Thanks for your remark..

    It shure was fun to do. And if you have questions about this subject, don't hessitate to ask!
    That is what these forums are about! To shine light on what others want to know..

    all the best,

    Ra.
    Last edited by koti; 01-12-2009 at 06:03 PM.

  3. #243
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    Default Re: Optic theory

    Ra,

    As for real questions, I have one.
    I dont want to make an idiot out of myself but here it goes :

    If I have 2 flashlights with identical emiters and identicaly polished reflectors of same material (with the same circumference at the widest point) where one reflector has a larger "shine" area than the other, then the flashlight with the larger area reflector will give more throw ?
    More simplified...if one of the reflectors is more "cone shaped" then "disc shaped" (has a larger area) then it will give more "throw"
    If not, Im going to read the whole thread again and try to understand...

  4. #244

    Default Re: Optic theory

    The deeper reflector gives a larger spot (smaller f), but both have the same throw (same lux at the spot center) because they are the same diameter. It's not the mirror area, but beam exit area.
    Now go reread the whole thread with the remaining good eye ;-)

  5. #245
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    Default Re: Optic theory

    If both have the same lux, or throw, then the one with the larger hotspot will illuminate more at distance, and appear to have more throw.

    Bill

  6. #246

    Default Re: Optic theory

    More but not farther.
    Will appear to have more spot (perhaps less spottable, less edge contrast), but won't throw farther. A distant observer couldn't tell them apart.

    If you want, more at distance (spot), but not at more distance (throw). Flux vs lux. Quantity and quality.

  7. #247
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    Default Re: Optic theory

    Not further - agreed.
    But deeper reflector will be brighter then a shalow reflector, right ?
    Whats the reason behid putting deep reflectors into flashlights anyway ?
    Oh and...its not the eye...its the green thing attached to it in the back I guess.
    Last edited by koti; 01-14-2009 at 03:31 AM.

  8. #248

    Default Re: Optic theory

    "Whats the reason behid putting deep reflectors into flashlights anyway ?"
    To control the spot/spill ratio. More spot, less spill.

    You seem to be confused by the fact that the mirror has more area. Try this: do you see a bulb vary brightness as you look at it in a tilting hand mirror? I guess not, same image. But as you tilt it more you're using more area of the mirror, no? I think yes.

  9. #249
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    Default Re: Optic theory

    Quote Originally Posted by zzonbi View Post
    "Whats the reason behid putting deep reflectors into flashlights anyway ?"
    To control the spot/spill ratio. More spot, less spill.

    You seem to be confused by the fact that the mirror has more area. Try this: do you see a bulb vary brightness as you look at it in a tilting hand mirror? I guess not, same image. But as you tilt it more you're using more area of the mirror, no? I think yes.

    So the deeper the reflector the more focused the beam - which is logical to me. But this has to mean more throw which I think is totaly oppposite to what RA was saying all along this thread ?!

    A tilting hand mirror doesnt focus light therefore I would leave it out because I moght get too confused and my head could

  10. #250

    Default Re: Optic theory

    Quote Originally Posted by koti View Post
    So the deeper the reflector the more focused the beam - which is logical to me. But this has to mean more throw which I think is totaly oppposite to what RA was saying all along this thread ?!

    A tilting hand mirror doesnt focus light therefore I would leave it out because I moght get too confused and my head could
    The deeper reflector does two things when compared to a reflector of the same diameter. It captures and collimates more of the light output from the LED. And what it does capture on the "extra" portion of reflector is more collimated thus leading to more throw. The farther away from the source the reflecting surface is the better collimated the resulting beam will be because at that farther spot the source will "look" smaller and more point source. This makes for more throw and is why you see the thrower lights getting deeper and deeper reflectors in an attempt to one-up the other. Ra's posts don't make sense and I stopped listening to him a while back. Not trying to start a fight Ra, just saying.

  11. #251
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    Default Re: Optic theory

    Now Im realy confused.
    This is a lot of contradiction - I will have to read thru the whole thing again when I have time and rethink all this.
    Im sure of one thing though...What Ra's is saying and what saabluster (and others) are saying contradicts totaly so this is not exhausted.

    Im thinking...why do throwers have deep reflectors?
    If what Ra's saying is coprrect then we should have tiny monster throwers available, why dont we have them ?

    Also...if something is brtighter then doesnt it mean that it will throw further ? I mean...if You have 2 identical flashlights with identical reflectors only with different emiters (one stronger then the other) then surely one of the flashlights will be both brighter and have more (a little more) throw ?

    This is all weird...

  12. #252

    Default Re: Optic theory

    "So the deeper the reflector the more focused the beam"
    I just said the larger the spot. Despite more reflected light maximal brightness is the same, except for minor differences caused by the smaller non emitting focal plane (the flat disc in plane with the die).

    "If what Ra's saying is coprrect then we should have tiny monster throwers"
    And we don't have them because it is correct: you need large diameters (easy) or high led brightness (not so easy, therefore Ra uses an arc lamp). Or 'cheat' with the laser effect.

    Now you have all the cards. You need to decide yourself what is correct. Good luck.

    PS I must remind that this theory applies to uniform or lambertian sources. Sources packaged in altering optics may skew the results one way or the other.
    eg leds with beam tightening packages could hardly give a spot from a shallow reflector, a batwing profile may send less light to the edge of a deep one.
    Last edited by zzonbi; 01-15-2009 at 08:31 PM.

  13. #253
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    Default Re: Optic theory

    proud Fenix T1 aspheric R2 owner

  14. #254

    Default Re: Optic theory

    Quote Originally Posted by Nos View Post
    Do you have something to add here? If not why the bump? This isn't a sale thread.

  15. #255
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    Default Re: Optic theory

    Quote Originally Posted by saabluster View Post
    Do you have something to add here? If not why the bump? This isn't a sale thread.
    Yes, bunping is usually used in sales threads. I think that Nos really wants to know if there is any new info available since the last post in January?

    Bill

  16. #256
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    Default Re: Optic theory

    Yeah, I got something to add...
    Im too dumb and lazy too analize this whole thread from scratch plus there seems to be lack of a clear goal in all the talking, but...
    If "Ra" is talking crap then how come he built the longest throwing flashlight existing on this forum ? He built it 2 years ago and still noone beat his achievement. Thats gotta count for something...

  17. #257

    Default Re: Optic theory

    Quote Originally Posted by koti View Post
    Yeah, I got something to add...
    Im too dumb and lazy too analize this whole thread from scratch plus there seems to be lack of a clear goal in all the talking, but...
    If "Ra" is talking crap then how come he built the longest throwing flashlight existing on this forum ? He built it 2 years ago and still noone beat his achievement. Thats gotta count for something...
    So what. I made the longest throwing LED flashlight by far but it doesn't mean I know anything.

  18. #258
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    Nana Re: Optic theory

    It has been a long time, finaly found some free time to read thru the Ra portion of this thread again...

    I think that Ra's statements are all correct, couldnt find any contradictions. Maybe they are incomplete though ?

    I just want to know why a Deerelight DBS thrower has this reflector:



    instead of this reflector :




    Ra please excuse my ignorance and lack of knowledge but could You please answer this simple question for me ?

  19. #259
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    Default Re: Optic theory

    Quote Originally Posted by koti View Post
    It has been a long time, finaly found some free time to read thru the Ra portion of this thread again...

    I think that Ra's statements are all correct, couldnt find any contradictions. Maybe they are incomplete though ?

    I just want to know why a Deerelight DBS thrower has this reflector:



    instead of this reflector :




    Ra please excuse my ignorance and lack of knowledge but could You please answer this simple question for me ?
    I think the answer is so that the spot is big enough to see at a great distance (throw). The depth is so it doesn't look like a laser (pinpoint) and the reflector diameter along with the emitter provides the brightness (throw).
    Last edited by gcbryan; 02-08-2010 at 03:24 PM.

  20. #260
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    Default Re: Optic theory

    I think the answer is so that the spot is big enough to see at a great distance (throw).
    This doesnt make sense to me...the spot in throwers is narrow in order to throw further. If it was big like You say, a thrower would not throw far. Besides the deepness of the reflector does not effect the size of the spot, the deepness of the reflector affects the amount of collected lumens from the source.
    The depth is so it doesn't look like a laser (pinpoint)
    So are You saying that if the DBS reflector was very shallow the light would look similar to a laser? I dont think so...
    and the reflector diameter along with the emitter provides the brightness (throw).
    According to Ra, the diameter of the reflector along with the surface brightness of the source will affect throw. Brightess and throw are 2 totaly different things. But Your last sentence seems correct

    Here are some quotes by Ra :

    #7
    That is why the lens- or reflector-diameter determines the throw of a torch. (together with the surface brightness of the source)


    #20
    You are propably not going to beleve what I'm going to tell you now: THROW IS ABSOLUTELY NOT AFFECTED BY THE FOCAL LENGTH OF THE REFLECTOR OR LENS !! ONLY LUMENS OUTPUT IS !!

    FACT: The apparent surface brightness of the reflector cannot ever be higher than the surface brightness of the source! It always is lower due to reflection losses in the reflector.

    #123
    So, For you, and everyone who didn't know this: A learning moment:

    THROW IS DETERMINED BY THE DIAMETER AND EFFICIECNY OF YOUR LENS OR REFLECTOR and THE SURFACE BRIGHTNESS OF YOUR LIGHTSOURCE.
    LUMENS OUTPUT IS DETERMINED BY THE DIAMETER AND EFFICIENCY OF YOUR LENS OR REFLECTOR and THE FOCAL-RATIO OF YOUR LENS OR REFLECTOR

    I dont understand why literaly all throwers have deep reflectors...why is that if according to Ra, throw has nothing to do with the deepness of the reflector?

  21. #261

    Default Re: Optic theory

    Quote Originally Posted by koti View Post
    I dont understand why literaly all throwers have deep reflectors...why is that if according to Ra, throw has nothing to do with the deepness of the reflector?
    Well...
    If you look at it practiaclly: Your LED has an emittance pattern. The reflector diameter and the source size determine the hotspot diameter.
    The deepness determines how much of the lumens of the light actually hit the reflector.
    (leds are anisotrophic emitters)

  22. #262
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    Default Re: Optic theory

    Quote Originally Posted by IMSabbel View Post
    Well...
    If you look at it practiaclly: Your LED has an emittance pattern. The reflector diameter and the source size determine the hotspot diameter.
    The deepness determines how much of the lumens of the light actually hit the reflector.
    (leds are anisotrophic emitters)
    What pattern are You reffering to, placement of photons along the viewing angle? Photon density pattern?
    The reflector diameter does NOT determine the the hotspot diameter...at least thats what Ra is saying...
    The deepnes of the reflector determines the amount of lumens that hit the reflector? Thats weird...
    If LED's are "anistropic" then filanment sources are "isotropic" ?
    That may be true since LED's are more directionaly dependent than bulbs but I dont see how that corelates to my question.

  23. #263
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    Default Re: Optic theory

    I'd like to see RA return to this thread!

    I (now) think that the diameter (along with the emitter) determines how tightly focused the hotspot is and therefore how intense. I think that depth (to a degree) does the same thing by redirecting more lumens from spill to the hotspot.

    I'm still not clear as to how RA would address this issue. I'm still not clear as to whether depth in addition to redirecting more lumens to the hotspot is also resulting in more collimated rays due to the increasing distance (more point source like). I'd like to hear RA's take on this.
    Last edited by gcbryan; 06-15-2010 at 01:23 AM.

  24. #264
    Flashaholic* Ra's Avatar
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    Default Re: Optic theory

    Ok then, Here I am !!

    Some of you exactly know what this is all about, but are still quite easily forced into doubt by others..
    For example zzonby is exactly right:

    With the same lightsource, throw is absolutely not affected by the deepnees of the reflector!! If it is affected, it's caused by other things like difference in surface quality of the reflector, or reflectivity of the reflection layer.

    Yes: Deeper reflectors produce a wider beam, why?: Because they simply grab more emmitted lumens from the source, because they are more 'folded' around the source..

    No: Deeper reflectors do not produce more throw because the apparent surface-brightness of the reflector remains the same. Note that this only involves reflectors with the same diameter !!

    Important: These are theoretics, based on using the same source in both situations and using perfectly formed parabolic reflectors!

    Why do few people actually measure otherwise: Shallow reflectors need to be more precisely formed than deep reflectors, in order to be totally lit by the source for an object far away.. You first need to be certain of the quality of the stuff you tend to use, before putting the theory to the test.. Beleve me: I've done it, and things behaved exactly as theory predicts..

    Fact: Look in the reflector from a distance more than 50 meters, with the torch operating (use heavy sunglasses or a welding filter) Now if the reflector does not seem to be fully lit, you are not effectively using it. The shape can be wrong or you simply need to focus the reflector till it is fully lit.

    Now take two situations: Deep reflector, and shallow reflector.. Both clearly fully lit by the source when you look at them from a distance of 50 meters or more..
    Now try to tell wether you are looking at the shallow reflector, or the deeper one..

    Let me tell you the result: YOU CAN'T !!.. Both reflectors seem equally bright. This also means that for the exact spot where you're standing that moment, the lux reading will be (more or less..) the same for both reflectors.

    Only if you begin to move sideway's, the shallow reflector will be first in loosing effectivity, it will no longer be fully lit

    The gain in wideness of the spot with the deeper reflector only comes from the fact that you grab more lumens from the source, which is evenly spread, further away from the center of the spot..


    Sorry, I cannot be more clear than this at the moment..

    If you have questions, post them here, I'll answer them (if I know the answers ofcource..)


    Regards,

    Ra.
    Last edited by Ra; 06-15-2010 at 02:01 PM.
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  25. #265
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    Popcorn Re: Optic theory

    Quote Originally Posted by saabluster View Post
    So what. I made the longest throwing LED flashlight by far but it doesn't mean I know anything.

    Wait till I really am going to design a LED-thrower... Could be in a few day's, or weeks, even month's.. But my (second..) time of glory will come..


    Regards,

    Ra.
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  26. #266
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    Default Re: Optic theory

    Thanks RA.

    So, just to clarify (I know it's obvious at this point but bear with me please)...

    The reasons that lights that are considered to be "throwers" frequently are deep as well as wide are...

    1. They have to keep the shape of a parabola so since they will have larger diameters (as opposed to a non-thrower) the depth will increase as well if for no other reason than for that reason.

    2. Since the spot becomes more narrow and intense (tightly focused) with increasing diameter reflector depth is frequently increased to make the hotspot a little more useful at less than max throw.

    Are those two statements more or less accurate?

    Also, I have a reflectored thrower (Uniquefire HS-802) that has a reflector diameter of approximately 45 mm and a depth of approximately 56 mm. It uses a XR-E R2 driven at 1A. The hotspot seems (to me) very small even though the depth is relatively large.

    The explanation for this (I know you don't have this light in front of you) would be that without the depth the spot would be even smaller?

    Would that be correct?

    Thanks again for coming back to clear up a few aspects of this subject. This thread was clear to a point with what throw is but didn't address as clearly the question of why do many throwers have deep reflectors if it's not related to throw.

    Thanks for clearing this up.

  27. #267
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    Popcorn Re: Optic theory

    Quote Originally Posted by koti View Post
    Not further - agreed.
    But deeper reflector will be brighter then a shalow reflector, right ?
    Whats the reason behid putting deep reflectors into flashlights anyway ?
    Oh and...its not the eye...its the green thing attached to it in the back I guess.
    Yep, a deeper reflector will be brighter, but only in lumens output, and more lumens does not nesseseraly mean more throw.. Definitely not when the reflector diameter does not change..

    So the reason for putting deep reflectors into flashlights is obvious: By putting more lumens from the source into the main beam, you get a better compromise between throw and sidespill. Simply improving the efficiancy of the torch..

    This is most true for LED's: Led's are front emitting.. The standard conventional reflectors are initially designed for side emmiting sources (Xenon-, normal or halogen light bulbs)
    So when you use a led with a conventional reflector, you need a very deep one: The led emits most of the light strait forward, so even with the deepest reflector, most of the light still is not collimated within the main beam.

    That's why led's work better with aspheric lenses: With an aspheric lens, you grab most of the light emitted directly in front of the led..

    But no aspheric lens, or reflector can match the collimating power of a TIR optic !!

    With a TIR, you can grab up to 95% of all the lumens a led emits, and put those lumens into a nicely collimated, but ofcource more sidespilled beam.


    Regards,

    Ra.
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  28. #268
    Flashaholic* Ra's Avatar
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    Default Re: Optic theory

    Quote Originally Posted by gcbryan View Post
    Thanks RA.

    So, just to clarify (I know it's obvious at this point but bear with me please)...

    The reasons that lights that are considered to be "throwers" frequently are deep as well as wide are...

    1. They have to keep the shape of a parabola so since they will have larger diameters (as opposed to a non-thrower) the depth will increase as well if for no other reason than for that reason.

    2. Since the spot becomes more narrow and intense (tightly focused) with increasing diameter reflector depth is frequently increased to make the hotspot a little more useful at less than max throw.

    Are those two statements more or less accurate?

    Also, I have a reflectored thrower (Uniquefire HS-802) that has a reflector diameter of approximately 45 mm and a depth of approximately 56 mm. It uses a XR-E R2 driven at 1A. The hotspot seems (to me) very small even though the depth is relatively large.

    The explanation for this (I know you don't have this light in front of you) would be that without the depth the spot would be even smaller?

    Would that be correct?

    Thanks again for coming back to clear up a few aspects of this subject. This thread was clear to a point with what throw is but didn't address as clearly the question of why do many throwers have deep reflectors if it's not related to throw.

    Thanks for clearing this up.
    Sorry gcbryan,

    I noticed you posted just before me..

    You are exactly right..

    One remark about your point nr 2 tho: Increasing the reflector diameter increases the brightness at the center of the spot, so in fact, the spotsize doesn't change. It only seems smaller because the sidespill is pushed to the background by the brighter center of the spot. The sidespill doesn't change in brightness, so is more overpowered by the hotter center of the beam.

    If something faint commes close to something bright, it seems to become fainter..



    EDIT: That means if you use a deeper reflector with the same diameter, the brightness of the center of the spot does not change, but the extra amount of lumens you grab from the source will create more sidespill around the center of the spot..

    EDIT nr2: Especially with a CREE, a conventional reflector is very inefficient, like I said in my earlier post. The Cree already has a kind of collimating lens (glass dome) which narrowes the emittance angle to a mere 145 degrees.. More suitable for use with an aspheric lens, not with a conventional reflector..





    Regards,

    Ra.
    Last edited by Ra; 06-15-2010 at 04:25 PM.
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  29. #269
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    Default Re: Optic theory

    When you use the term "sidespill" you mean that in a way that is different than our use of the term "spill" correct?

    I consider "spill" as that light that doesn't hit the reflector but rather just comes straight out (uncollimated) from the emitter.

    1). You are using "sidespill" to mean that light in the hotspot that isn't the most highly collimated light in the very center...correct?

    2). Also, although TIR is more efficient it's not going to provide the most throw and isn't practical in the larger sizes...correct?

    I like TIR as well and wish it was used in most flashlights (all but the dedicated throwers).

    3). You mentioned that increasing the diameter of a reflector increases the intensity but doesn't actually change the hotspot size. What does? It's a matter of the emitter size and what else? I assume it's just reflector shape? Some reflectors have a larger flat spot next to the emitter. Is that it?

    4). What is the relationship with an aspheric between intensity and increasing the diameter. If you go from a diameter of 30 mm to 60 mm if lux at 1 meter for the 30 mm was 15,000 lux what would the expected lux be for the 60 mm diameter optic?
    Last edited by gcbryan; 06-15-2010 at 05:47 PM.

  30. #270

    Default Re: Optic theory

    Quote Originally Posted by Ra View Post
    Wait till I really am going to design a LED-thrower... Could be in a few day's, or weeks, even month's.. But my (second..) time of glory will come..


    Regards,

    Ra.
    I look forward to it. With your skills making TIR optics I suppose you are going to go down that route? Should be interesting. Working on a little something-something myself. Who knows when I will be able to complete it though. One thing that has not really been done yet is a large format LED spotlight. You thinking about something like that or do you want to keep it as a true flashlight?

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