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Biological reasons for color perception

Ablaze

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I'm trying to figure out why our eyes work the way they do in respect to color. What mechanism makes us see green so brightly? I have heard quite a few smart people with something to say about it, but a lot of what I have heard is contradictory.

I was looking at this site recently, which has some good information, but not enough information to really explain the perceived color differences.

Does anyone have any other good resources about this (that are not wikipedia)?
 

qumefox

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I think this is likely one of those questions that there really isn't a good easy answer too. It's like "why do cat's have tails?"

It just boils down to evolution.
 
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For humans I think it would have to due with primates and how they stayed in trees and well trees are green so you'd want to see the leaves well VS the fruit which could be red, blue, or yellow. It's just a adaptation humans got from our ancestors. It just makes sense when you think about it.
 

honeyx

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IIRC it´s because it´s in the middle of the visible spectrum and because the very first algae on earth were red absorbing green the best. They absorbed all the green in the ocean so all the other organisms living there had to deal with the left red and blue. Thats also why later green algaes developed absorbing red and blue the best and became dominant.

Don´t remember how this has an influence to more complex organisms who developed eyes, but like qumefox said it boils down to evolution.
 

Ablaze

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So anyway, I'm still trying to understand this.

I found an equation here on luminous flux. I like luminous flux, and would like to describe all my lasers in terms of how many lumens they produce. This would be a description of how bright the laser appears, which I would find much more practical than the mw output.

Unfortunately this equation leaves out several key variables, like how Φ * Vλ is defined for a particular wavelength. Does anyone know a formula for lumens that can be applied to lasers?
 

qumefox

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If you want to know the luminous power just install chroma and plug in the wavelengths and powers in question.

However 'lumens' isn't really the appropriate terminology to describe lasers.
 
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qumefox

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Ohh yeah? Why do you consider a lumen inappropriate?
Because it has no direct relation to the actual power of a laser and in the long run will only serve to confuse people and we'll start getting questions like 'how many lumen does it take to burn' and the like...

It's useful to an extent for color mixing, but beyond the world of display, relative brightness matters little here.
 

Ablaze

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Because it has no direct relation to the actual power of a laser and in the long run will only serve to confuse people and we'll start getting questions like 'how many lumen does it take to burn' and the like...

It's useful to an extent for color mixing, but beyond the world of display, relative brightness matters little here.
It seems to me to be the other way around. There are a lot of questions that people ask that could be answered much more easily in lumens than mw. For instance, when someone says "I want a laser that goes further than my 200mw green,". Wouldn't it be simpler to just say "that's 7000 lumens, so find something with more lumens than 7000"?

It seems to me that the only way in which mw is a better measurement is when you are trying to judge burning power. In any other circumstance I think people would find lumens more useful.
 
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your post just brought up a good point ablaze

how far will my laser go ? we get those on a steady basis.. will a 250mw laser really go farther than a 200mw laser? i thought it was more based on atmospheric conditions. i mean im sure brightness has a factor but just because you don't see it, doesn't mean it has disappeared, right?
 

qumefox

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The answer to 'how far' any laser goes is 'forever, until the photons hit something'. Power has nothing to do with that. and the apparent 'vanishing point' say shining it up in the air, will also look exactly the same distance regardless of if it's 5mW or 500mW.
 
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The answer to 'how far' any laser goes is 'forever, until the photons hit something'. Power has nothing to do with that. and the apparent 'vanishing point' say shining it up in the air, will also look exactly the same distance regardless of if it's 5mW or 500mW.
thats what i thought i had been told before and it makes plenty of sense. thank you for the confirmation man :thanks:

i mean the photons dont just disappear :p
 
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Ablaze

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The answer to 'how far' any laser goes is 'forever, until the photons hit something'. Power has nothing to do with that. and the apparent 'vanishing point' say shining it up in the air, will also look exactly the same distance regardless of if it's 5mW or 500mW.
Yes, but people still ask.

If we measured more light sources in lumens the world would be a (slightly) better place. For instance: vehicle headlights. If the maximum output was in lumens rather than watts then people couldn't play with the color and blind other drivers.

Also, lightbulbs. If the light bulbs had been measured in lumens all along we wouldn't have to put up with "100 watt equivalent" for florescent bulbs.

Back to topic.. madmac, I understand your overview of what a lumen is, however what I'm really looking for is an equation: given nm and mw, what is output in lumens. Thank you for the info anyway.
 

lasersbee

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Yes, but people still ask.

If we measured more light sources in lumens the world would be a (slightly) better place. For instance: vehicle headlights. If the maximum output was in lumens rather than watts then people couldn't play with the color and blind other drivers.

Also, lightbulbs. If the light bulbs had been measured in lumens all along we wouldn't have to put up with "100 watt equivalent" for florescent bulbs.

Back to topic.. madmac, I understand your overview of what a lumen is, however what I'm really looking for is an equation: given nm and mw, what is output in lumens. Thank you for the info anyway.
Look at his graph... the info you seek is there...:undecided:
BTW... How do you figure my world would be a better place...:thinking:
Makes no difference to me..
Knowing if my car is traveling at 100Mph or 160Kph or if it is
checked by the time it takes to travel from one hydro pole to
the other will not make my world any better.

Not every human eye is identical...


Jerry
 




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