Are lights additive?

[Weep]

Light is additive. Shine two of the same kind of light on a surface, and it will have two times the amount of light hitting it and reflecting. Simple as that.

Well...not quite. Cameras and eyes see light roughly logarithmically. Anyone familiar with photography should know about the concept of "stops" or "exposure values". In short, each doubling of light appears like one step of brightness increase. The difference between 20 lumens and 40 lumens would appear to be about the same as the difference between 160 and 320 lumens. It's not linear, it's perceived as relative.

As for colored light, yes, colored light adds. That's how nearly any computer screen works - it has small colored dots of red, green, and blue. Red, green, and blue, when added (either by shining those colors on the same spot, or having very small emitters very close together like on a screen) will look like white. It's not a full spectrum of wavelengths like sunlight, but it will look white since it stimulates the color receptors in our eyes equally. Red + green = yellow, green + blue = turquoise/cyan, blue + red = magenta. (Yep, it's different than paint or inks.)

 

[Mark2]

If multiple light sources wouldn't add up, then lights such as the Inova X5 would be pretty stupid designs. /ubbthreads/images/graemlins/smile.gif

Forgot to mention: I actually did the test with the light meter and they *do* add up.

 

[chmsam]

Weep had the perception part correct. Our eyes only perceive increases in lighting level in increments. Example: the light from six candles will appear brighter than one, but the light from ten or eleven candles doesn't necessarily appear any brighter than from nine. There is a threshold that the level must pass so our eyes and brain can perceive it. That's why we use measuring devices -- it's harder to fool them. All of our senses have a difference between perception and actual, measureable change. That gets confusing for most people.

 

[daloosh]

Nice explanation Weep, interesting discussion you prompted archangel, welcome to CPF and why dontcha stay awhile, you too, powerful_dark!

daloosh

 

[elgarak]

Interferometers do not cancel out light from two different sources (as McGizmo suggested as something similar to sound cancelling headphones). They split light from one source into two beams, and then superimpose the two beams. Or in astronomy, the light/radio wave from one source (star, quasar etc.) is measured with two telescopes and then superimposed (optically, by superimposing the light beams of two telescopes nearby; in the case of radio waves logically/mathematically with the computer, using data recordings from different, even very far apart, radio telescopes).

Nice experiment for everyone to try out (the usual safety rules when handling lasers apply!): Take a CD and shine your laserpointer on it. The laser beam is reflected in the different data pits, and thereby split. Since the data pits are at slightly different positions, the reflected light from two different data pits cancel each other out in most directions. Only in very few directions light is reflected. If you use a red laser, you'll get the interference pattern from the tracks. With a green laser, the wavelength is small enough to also resolve the pits inside each track. You'll get the same interference pattern of the tracks (with spots faily far apart), but each spot is comprised of small dots/lines very close to each other.

 

[Lexus]

Are lights additive?
My lightmeter says: Yes!

Are lights addictive?
My credit card says: Yes! /ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/help.gif /ubbthreads/images/graemlins/broke.gif

EDIT: Sorry for hijacking /ubbthreads/images/graemlins/tongue.gif

 

[daloosh]

Lexus, that's why I first tuned into this thread, I thought the poster forgot the c in "addictive" and this was about buying too many lights, not about adding LEDs! LOL!

daloosh

 

[UVvis]

The problem with the human eye is each detector (entire eye) is different. I can see in wavelengths with my right eye that I can't with my left.

Almost anything can be a source of polarized radiation. You need a polarized filter to reduce the rest angles you don't need. Like if you have polarized sunglasses and you turn your head at different angles to asphalt roads you see different amounts of glare. Of if you take two good polarized filter lenses, and get them at 90degrees alignment of each other you are effectively blocking all light that the filters effect.

 

[NikolaTesla]

More Lux III's is way better than one, I can tell you that with out any math or meters or I wasted a lot of and time and money on this:

Even a SureFire L6 or Aleph 3 with U bin at 1000 MA does not hold a candle to it. MORE is better.

 

[cognitivefun]

I think they are. I've become quite addited to lights.

 

[powerfuldark]

[ QUOTE ]
Wouldn't the brightness of the higher powered light "overtake" the brightness of the lower powered LED?

[/ QUOTE ]

Where do I possibly begin with this one?

[ QUOTE ]
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?


[/ QUOTE ]

Are you suggesting that different beams of light travel at different velocities based on the strength of the beam? All electromagnetic radiation, of which visible light represents a small part, propogates at the same velocity, c . A man acheived a certain degree of fame in 1905, when he concluded that this speed is independent of the observer, a fact which may keep you up at night.

[ QUOTE ]
Yeah, let's aim the lights at each other and see if it subtracts!

[/ QUOTE ]

Actually, any wave will be canceled by a similar wave that is 180 degrees out of phase. For all practical purposes, this may be ignored for the situation at hand.

 

[Sigman]

powerfuldark...don't "read" too much into my comments - can't a fellow just have a "good time"? /ubbthreads/images/graemlins/grin.gif

Additionally, I meant no disrespect to archangel - I knew the question would get answered...I just didn't have the solution! /ubbthreads/images/graemlins/grin.gif

:sorry:

 

[nikon]

[ QUOTE ]
powerfuldark said:
[ QUOTE ]
Are you suggesting that different beams of light travel at different velocities based on the strength of the beam? All electromagnetic radiation, of which visible light represents a small part, propogates at the same velocity, c . A man acheived a certain degree of fame in 1905, when he concluded that this speed is independent of the observer, a fact which may keep you up at night.

[/ QUOTE ]


I'm glad you brought up the speed of light because there's a question that's been bugging me for years. If you're travelling at the speed of light and you turn your flashlight on, would the photons bunch up in the reflector or would they fall to the floor?

 

[elgarak]

[ QUOTE ]
I'm glad you brought up the speed of light because there's a question that's been bugging me for years. If you're travelling at the speed of light and you turn your flashlight on, would the photons bunch up in the reflector or would they fall to the floor?

[/ QUOTE ]

Neither. First, you cannot travel with the speed of light. But assuming you would travel close to it, you would still measure the photons as leaving your light with the speed of light. Your twin brother, who is standing still, would measure the same speed of light for the photons emitted from your flashlight (travelling close to the speed of light). Ahhh, wonderful confusing world of relativity!

 

[UVvis]

Some of the ones from my light and quantum physics courses from way back that a vaguely remember. The sad thing is that someone will probably post answers shortly.

How fast do you have to be taveling for a red stop light to appear green in colour? This one was with, how fast do I have to travel for my 22ft long lincoln to fit into my 16ft long garage?

I recall doing calculations for light beam cancellation with layers of material with different refractive indexes, such as anti-reflective light cancelling layers.

 

[powerfuldark]

[ QUOTE ]
how fast do I have to travel for my 22ft long lincoln to fit into my 16ft long garage?


[/ QUOTE ]

A quick in-my-head approximation would be 460 million mph, or a little less than 0.7 c.

And you thought you guys were a bunch of geeks.