Or do you need to use inverse-square (or whatever it's called)? In other words, if i have a torch of brightness 3 and a torch of brightness 4, is that equivalent to a torch of brightness 7, or is it closer to 5 (the square root of 3-squared + 4-squared)? I assume the same property would apply to torches with more than one LED.
Are lights additive?
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powerfuldark
Newly Enlightened
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Someone failed math. /ubbthreads/images/graemlins/jpshakehead.gif
cheapo
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Sigman
* The Arctic Moderator *
If you are asking this? You have a light with a 4 lux reading and a light with a 3 lux reading...turn them both on and aim them at a light meter.
You will not read anything over the brightest reading of the brightest light. In other words you will read 4 lux. They will not "add" together.
You will not read anything over the brightest reading of the brightest light. In other words you will read 4 lux. They will not "add" together.
cheapo
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Really Sigman, I didnt know that. That is weird. You'de think that added output means added throw.
-David
-David
I am betting there will be a little *adding* of the two beams but most likely the 4+3 lux combination would end up reading about 4.1-4.3 lux instead and a lot of that would be equated to the area read by the luxmeter. If the area read is large enough the defects in the beams would overlap and a dim spot in the brighter light could be filled by the dimmer one bringing the light level up some.
I hope my logic is correct as I have seen the same idea used in multiple 5mm LED lights. A single LED is blasted away by a 5 LED light.
I hope my logic is correct as I have seen the same idea used in multiple 5mm LED lights. A single LED is blasted away by a 5 LED light.
What do you mean they won't add?!?! So then if you take a 5W LED that has four dies then you can power down one of the dies at a time until you are only running one and the light will still have the same lux?!?!? Uh, I would like to suggest that a light meter reads light that is reaching it and if you add light to it from another light, you will see it increase. /ubbthreads/images/graemlins/thinking.gif
EDIT: I saw the subject and it was in line with a Q I wanted to ask so I'll add it on here. /ubbthreads/images/graemlins/smile.gif (hope no one minds)
Now I know if you take a narrow band of red, green and blue LED's and mix them properly, you will see white light bounced back from a white wall. Now, what happens if the wall is a perfect yellow. You are not hitting the wall with full spectrum light from which yellow light could be reflected. You are hitting it with red, green and blue. Do the red and green mix on the way in and therefore return as yellow light reflected from the yellow wall? Is a yellow wall yellow because it rejects all but yellow light or is it yellow because it likes to reflect both red and green light in a certain porportion? Would the yellow wall look the same and be the same brightness if it were bathed in a yellow band light source of equal flux to the combined red and green bands? How do colors work? /ubbthreads/images/graemlins/icon15.gif
EDIT: I saw the subject and it was in line with a Q I wanted to ask so I'll add it on here. /ubbthreads/images/graemlins/smile.gif (hope no one minds)
Now I know if you take a narrow band of red, green and blue LED's and mix them properly, you will see white light bounced back from a white wall. Now, what happens if the wall is a perfect yellow. You are not hitting the wall with full spectrum light from which yellow light could be reflected. You are hitting it with red, green and blue. Do the red and green mix on the way in and therefore return as yellow light reflected from the yellow wall? Is a yellow wall yellow because it rejects all but yellow light or is it yellow because it likes to reflect both red and green light in a certain porportion? Would the yellow wall look the same and be the same brightness if it were bathed in a yellow band light source of equal flux to the combined red and green bands? How do colors work? /ubbthreads/images/graemlins/icon15.gif
powerfuldark
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[ QUOTE ]
McGizmo said:
What do you mean they won't add?!?! So then if you take a 5W LED that has four dies then you can power down one of the dies at a time until you are only running one and the light will still have the same lux?!?!? Uh, I would like to suggest that a light meter reads light that is reaching it and if you add light to it from another light, you will see it increase. /ubbthreads/images/graemlins/thinking.gif
[/ QUOTE ]
Phew! I thought it was me for a second.
Next thing we'll hear is that adding a second beam will make it dimmer. /ubbthreads/images/graemlins/ohgeez.gif
McGizmo said:
What do you mean they won't add?!?! So then if you take a 5W LED that has four dies then you can power down one of the dies at a time until you are only running one and the light will still have the same lux?!?!? Uh, I would like to suggest that a light meter reads light that is reaching it and if you add light to it from another light, you will see it increase. /ubbthreads/images/graemlins/thinking.gif
[/ QUOTE ]
Phew! I thought it was me for a second.
Next thing we'll hear is that adding a second beam will make it dimmer. /ubbthreads/images/graemlins/ohgeez.gif
adding more light will increase the light reflected back, and it will also increase the lux reading if both lights are aimed at the same point. I believe that if you aim two 100lux lights at a light meter, it will read very close to 200lux. This assumption does not account for the possibility of light wave cancellation.
Sigman
* The Arctic Moderator *
Wouldn't the brightness of the higher powered light "overtake" the brightness of the lower powered LED? Hmmmm, I don't know. I guess it's back to that, "I'm not a rocket scientist, nor have I ever played one on television...but I did stay at a Holiday Inn Express once". /ubbthreads/images/graemlins/grin.gif
It's like two vehicles racing in the same direction, if one is going 60 mph and the other is going 40 mph, the combined speed isn't 100. Now if they are headed towards each other and hit each other, then isn't that like a 100 mph collision?
Yeah, let's aim the lights at each other and see if it subtracts! /ubbthreads/images/graemlins/grin.gif
(I'm backing out of this one, even though it's too late for me! /ubbthreads/images/graemlins/grin.gif)
Seriously, just as is advertised on the box of the Nuwai Turbo 3x3 (which has a three way switch and allows one to light up 1, 2, or 3 LEDs at a time...well, not the one I just bought recently - but it's being replaced!)...
1 LED = 80 lux
2 LEDs = 160 lux
3 LEDs = 240 lux
(well that's what they claim)
So, yes they evidently do indeed add.
It's like two vehicles racing in the same direction, if one is going 60 mph and the other is going 40 mph, the combined speed isn't 100. Now if they are headed towards each other and hit each other, then isn't that like a 100 mph collision?
Yeah, let's aim the lights at each other and see if it subtracts! /ubbthreads/images/graemlins/grin.gif
(I'm backing out of this one, even though it's too late for me! /ubbthreads/images/graemlins/grin.gif)
Seriously, just as is advertised on the box of the Nuwai Turbo 3x3 (which has a three way switch and allows one to light up 1, 2, or 3 LEDs at a time...well, not the one I just bought recently - but it's being replaced!)...
1 LED = 80 lux
2 LEDs = 160 lux
3 LEDs = 240 lux
(well that's what they claim)
So, yes they evidently do indeed add.
Good job Sigman! /ubbthreads/images/graemlins/grinser2.gif
Now as to standing waves or cancelling, I suppose there may be something to it at a quantum level?!?! /ubbthreads/images/graemlins/icon15.gif At a practical level, does that mean I can tune my light to cancel out yours?!?! /ubbthreads/images/graemlins/grin.gif
Finally, I am still confused about colors!?!?!? I suppose I shouldn't be since I know that in the case of anodized Ti, there is no color in the anodize; it is merely a case of the light waves interfering with each other. Yeah, I know wave theory VS particle theory, right?!
OK, What if you shine a red light at a green light? Will the photons collide and become yellow?!?! /ubbthreads/images/graemlins/icon15.gif
Now as to standing waves or cancelling, I suppose there may be something to it at a quantum level?!?! /ubbthreads/images/graemlins/icon15.gif At a practical level, does that mean I can tune my light to cancel out yours?!?! /ubbthreads/images/graemlins/grin.gif
Finally, I am still confused about colors!?!?!? I suppose I shouldn't be since I know that in the case of anodized Ti, there is no color in the anodize; it is merely a case of the light waves interfering with each other. Yeah, I know wave theory VS particle theory, right?!
OK, What if you shine a red light at a green light? Will the photons collide and become yellow?!?! /ubbthreads/images/graemlins/icon15.gif
shifty is correct. Think of it this way: Light is produced as photons, small packets of energy. If you take two light sources, each of which generate 2000 photons per second, and you turn both of them on, you generate 4000 photons per second (twice the total flux, or twice the throw if both lights have the same geometry and aimed at the same target, which is sufficiently far away from both light sources). You can safely ignore interference or light wave cancellations or addition for all practical light sources -- even two lasers will not cancel each other out for observable effects.
McGizmo,
practically, you cannot use independent light sources to cancel each other out. First of all, white light consists of [Carl Sagan voice]billions and billions[/Carl Sagan voice] of photons of different energy or color. To cancel each energy, you have to find it exactly, which is not possible on a theoretical level (Heisenberg's Uncertainty Theorem). So you have to use two lights with exactly the same color. But then you also have to hit the right phase (think of two sine waves shifted against each other). Even photons from the same LED are out of phase, and are very difficult to use for interference experiments. The photons from two independent light sources are impossible. The only way to observe interference is using one laser, splitting the beam, do something to one of the beams, and put both of them together again into the same direction.
practically, you cannot use independent light sources to cancel each other out. First of all, white light consists of [Carl Sagan voice]billions and billions[/Carl Sagan voice] of photons of different energy or color. To cancel each energy, you have to find it exactly, which is not possible on a theoretical level (Heisenberg's Uncertainty Theorem). So you have to use two lights with exactly the same color. But then you also have to hit the right phase (think of two sine waves shifted against each other). Even photons from the same LED are out of phase, and are very difficult to use for interference experiments. The photons from two independent light sources are impossible. The only way to observe interference is using one laser, splitting the beam, do something to one of the beams, and put both of them together again into the same direction.
elgarak,
Thanks. I was reasonably certain that adding light was additive and that canceling out light was typically not something that happened. If it was, it would be used to effect. Since we have noise canceling headphones, who is to say what science won't come up with in regards to light.
For the sake of Sigman and others, with tongue in cheek, I tried to apply the brakes softly to this thread. In terms of adding light, it would be very difficult to visualize something to the contrary, IMHO. When Lloyd Bridges asked for every light they could find to be put on the runway, he had a reason! /ubbthreads/images/graemlins/grin.gif
Thanks. I was reasonably certain that adding light was additive and that canceling out light was typically not something that happened. If it was, it would be used to effect. Since we have noise canceling headphones, who is to say what science won't come up with in regards to light.
For the sake of Sigman and others, with tongue in cheek, I tried to apply the brakes softly to this thread. In terms of adding light, it would be very difficult to visualize something to the contrary, IMHO. When Lloyd Bridges asked for every light they could find to be put on the runway, he had a reason! /ubbthreads/images/graemlins/grin.gif
Sigman
* The Arctic Moderator *
Hey, I have my "moments" and must say, "I enjoy them"!! /ubbthreads/images/graemlins/grin.gif
(I was sitting here laughing and my wife walked by...had to explain "things" to her - oh boy, that didn't work - but I still had my chuckles!)
/ubbthreads/images/graemlins/thumbsup.gif
(I was sitting here laughing and my wife walked by...had to explain "things" to her - oh boy, that didn't work - but I still had my chuckles!)
/ubbthreads/images/graemlins/thumbsup.gif
/ubbthreads/images/graemlins/grin.gif Sigman, your days are just too long! Too much light! /ubbthreads/images/graemlins/tongue.gif
In regards to cancellation of light and stuff, I believe some ineresting things can be done with polarized light of which I believe sun light and possibly lasers are sources?
In regards to cancellation of light and stuff, I believe some ineresting things can be done with polarized light of which I believe sun light and possibly lasers are sources?
NewBie
*Retired*
[ QUOTE ]
McGizmo said:
elgarak,
Thanks. I was reasonably certain that adding light was additive and that canceling out light was typically not something that happened. If it was, it would be used to effect. Since we have noise canceling headphones, who is to say what science won't come up with in regards to light.
For the sake of Sigman and others, with tongue in cheek, I tried to apply the brakes softly to this thread. In terms of adding light, it would be very difficult to visualize something to the contrary, IMHO. When Lloyd Bridges asked for every light they could find to be put on the runway, he had a reason! /ubbthreads/images/graemlins/grin.gif
[/ QUOTE ]
Actually there is a device that uses light cancelation and peaks. It is often used to measure flatness, lens alignment, and various other things.
They are called Interferometers. You can use them to measure alignment or flatness to 1/10th of a wavelength or better, such as 0.000002492126 inches. They are alot of fun to use, and it is fun to watch 1" plate aluminum bend when you tighten a screw while watching...you can spend hours getting things to a nice alignment...
McGizmo said:
elgarak,
Thanks. I was reasonably certain that adding light was additive and that canceling out light was typically not something that happened. If it was, it would be used to effect. Since we have noise canceling headphones, who is to say what science won't come up with in regards to light.
For the sake of Sigman and others, with tongue in cheek, I tried to apply the brakes softly to this thread. In terms of adding light, it would be very difficult to visualize something to the contrary, IMHO. When Lloyd Bridges asked for every light they could find to be put on the runway, he had a reason! /ubbthreads/images/graemlins/grin.gif
[/ QUOTE ]
Actually there is a device that uses light cancelation and peaks. It is often used to measure flatness, lens alignment, and various other things.
They are called Interferometers. You can use them to measure alignment or flatness to 1/10th of a wavelength or better, such as 0.000002492126 inches. They are alot of fun to use, and it is fun to watch 1" plate aluminum bend when you tighten a screw while watching...you can spend hours getting things to a nice alignment...
Newbie,
I have heard of interferometers but always assumed that you needed to lift your hospital gown prior to their use. /ubbthreads/images/graemlins/nana.gif
(You get to play with too many cool devices! /ubbthreads/images/graemlins/grin.gif)
I have heard of interferometers but always assumed that you needed to lift your hospital gown prior to their use. /ubbthreads/images/graemlins/nana.gif
(You get to play with too many cool devices! /ubbthreads/images/graemlins/grin.gif)
bindibadgi
Flashlight Enthusiast
They're not always cool. They can be right royal pains in the pumpkin to align!
But, yeah, I guess they are cool. /ubbthreads/images/graemlins/wink.gif
But, yeah, I guess they are cool. /ubbthreads/images/graemlins/wink.gif
