On 9/17/2011 18:21, Tim Cook wrote:
> On 2011-09-17 08:47, Darren New wrote:
>> I think asking whether it's the eyes or the brain doing the
>> interpretation is an over-simplified question. :-)
>
> Well, was thinking more about the reception of the direct input from the
> rods and cones, separate any other processing. Sort of a..."is the colour I
> see as 'blue' the same colour you see as 'blue'?"

The different rods are definitely responding to different wavelengths. 
Whether the same wavelengths correspond to the same colors is a different 
and so-far-unanswered question.  I.e., "blue" is the same wavelength for 
everyone, but "blue" is a subjective experience.

-- 
Darren New, San Diego CA, USA (PST)
   How come I never get only one kudo?

Post a reply to this message

On 9/18/2011 0:51, Patrick Elliott wrote:
> None of us have a "name" for colors that contain
> both red and green in them,

And the fact that "magenta" as a wavelength does not exist, for example. :-) 
So we have names for colors that don't exist.

-- 
Darren New, San Diego CA, USA (PST)
   How come I never get only one kudo?

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> On 9/17/2011 18:21, Tim Cook wrote:
> > On 2011-09-17 08:47, Darren New wrote:
> >> I think asking whether it's the eyes or the brain doing the
> >> interpretation is an over-simplified question. :-)
> >
> > Well, was thinking more about the reception of the direct input from the
> > rods and cones, separate any other processing. Sort of a..."is the colour I
> > see as 'blue' the same colour you see as 'blue'?"

> The different rods are definitely responding to different wavelengths. 
> Whether the same wavelengths correspond to the same colors is a different 
> and so-far-unanswered question.  I.e., "blue" is the same wavelength for 
> everyone, but "blue" is a subjective experience.

  It becomes even more complicated when you consider that combinations of
different wavelengths may look the same to the human eye, yet may have
different physical properties (eg. when reflecting from surfaces).

  For example, a light consisting of one single wavelength, pure yellow,
may look to the human eye the exact same color as another light with two
wavelengths, a certain amount of pure red and a certain amount of pure
green. While these two types of light are, physically speaking, completely
different, they may look exactly the same to the human eye (ie. the second
light also looks pure yellow even though it has no yellow wavelength in it
at all).

  (The reason why we are able to see a pure yellow wavelength even though
we don't have "yellow" receptors is that the red and green receptors also
receive wavelengths from around those two wavelengths, including yellow.)

  Even though the two lights look the same color, they may illuminate
surfaces in different ways. That's because surfaces may reflect different
wavelengths in different ways. For example, if we had a surface that
reflected only the pure yellow wavelength, it would look yellow under
the first light but almost black under the second light. (That's the
reason why some lights make everything look "spooky" and unreal. This
is usually because they are composed of a combination of sharp wavelength
curves, rather than being an about evenly-distributed white light that
emits all visible wavelengths almost equally. "White" leds are a good
example of this.)

  Also, there's the fact that the human eye can perceive more colors than
a normal RGB monitor can emit (which means in practice that not all
photographs can be accurately presented with an RGB monitor).

-- 
                                                          - Warp

Post a reply to this message

> Darren New<dne### [at] sanrrcom>  wrote:
>> On 9/17/2011 18:21, Tim Cook wrote:
>>> On 2011-09-17 08:47, Darren New wrote:
>>>> I think asking whether it's the eyes or the brain doing the
>>>> interpretation is an over-simplified question. :-)
>>>
>>> Well, was thinking more about the reception of the direct input from the
>>> rods and cones, separate any other processing. Sort of a..."is the colour I
>>> see as 'blue' the same colour you see as 'blue'?"
>
>> The different rods are definitely responding to different wavelengths.
>> Whether the same wavelengths correspond to the same colors is a different
>> and so-far-unanswered question.  I.e., "blue" is the same wavelength for
>> everyone, but "blue" is a subjective experience.
>
>    It becomes even more complicated when you consider that combinations of
> different wavelengths may look the same to the human eye, yet may have
> different physical properties (eg. when reflecting from surfaces).
>
>    For example, a light consisting of one single wavelength, pure yellow,
> may look to the human eye the exact same color as another light with two
> wavelengths, a certain amount of pure red and a certain amount of pure
> green. While these two types of light are, physically speaking, completely
> different, they may look exactly the same to the human eye (ie. the second
> light also looks pure yellow even though it has no yellow wavelength in it
> at all).

Some persons will not see the red + green as yellow but rather as some 
shade of orange or yellowish green.

>
>    (The reason why we are able to see a pure yellow wavelength even though
> we don't have "yellow" receptors is that the red and green receptors also
> receive wavelengths from around those two wavelengths, including yellow.)

Some persond, mostly women, do have yellow receptors in addition to the 
usual red, green and blue ones.
It give them an edge in identifying plants and fruits.

>
>    Even though the two lights look the same color, they may illuminate
> surfaces in different ways. That's because surfaces may reflect different
> wavelengths in different ways. For example, if we had a surface that
> reflected only the pure yellow wavelength, it would look yellow under
> the first light but almost black under the second light. (That's the
> reason why some lights make everything look "spooky" and unreal. This
> is usually because they are composed of a combination of sharp wavelength
> curves, rather than being an about evenly-distributed white light that
> emits all visible wavelengths almost equally. "White" leds are a good
> example of this.)
>
>    Also, there's the fact that the human eye can perceive more colors than
> a normal RGB monitor can emit (which means in practice that not all
> photographs can be accurately presented with an RGB monitor).
>

Another example is the krypton headlight you find on some cars. They 
emit close to nothing in the yellow range. This makes some bright yellow 
cars appears as very dark gray.
Those also effectively suppress your night vision as they contains to 
much blue and violet.

Post a reply to this message

> On 2011-09-18 02:51, Patrick Elliott wrote:
>> Almost impossible to say. None of us have a "name" for colors that
>> contain both red and green in them, because, except for some situations
>> where you cause over-saturation, and some people "briefly" see a
>> confusing color that they normally don't, the processing basically robs
>> us of that range of colors. Some people, have four types of receptors,
>> so can see more colors, sort of, than we can, but without the "language"
>> to go with it, there is no way to process that into something tangible,
>> unless, by shear chance, a situation arose where someone "needed" to see
>> the differences, which is bloody unlikely. Otherwise, short of testing
>> it, there is no way to say precisely, save that it ranges from "not able
>> to see that color" to "everything is shifted slightly, so they don't see
>> some slice of the color range as clearly. I have no idea if certain
>> genetic forms produce a wider, or narrower, range, but that is likely,
>> so it could be shifted, or missing things on one end of the spectrum, or
>> the other, or both, etc.
>
> It occurs to me, however, a potential way to quantify the data. We have
> the ability to emit very specific wavelengths of light. We can,
> therefore, use a definite reference 'red', 'green', and 'blue', and
> calibrate a filtered sensor to each. This being done, we can use a very
> fine checkerboard pattern of the colours plus white, alternating with a
> pigment made by /mixing/ the colour plus white, thence other
> combinations. This would produce the baseline.
>
>  From here, it's a matter of detecting at the optic nerve what data gets
> sent on to the brain.

Been done, about 20 years ago...

>
> *whips out some nano-wires and a scalpel*
>
> Who's game? XD

If you take the signal just out of the eye and compare it to just after 
the optical nerve, you'll notice a significant difference. Don't forget 
that that nerve DOES have processing ability and do process the visual 
stream.

Post a reply to this message

On 9/18/2011 10:14, Alain wrote:
> If you take the signal just out of the eye and compare it to just after the
> optical nerve, you'll notice a significant difference. Don't forget that
> that nerve DOES have processing ability and do process the visual stream.

http://www.amazon.com/Brains-Men-Machines-Ernest-Kent/dp/0070341230

If anyone is interested in this topic, I highly recommend that book. It 
covers input, decision making, and output of the human body, expressed in 
layman's terms, with diagrams of (for example) op amps or simple digital 
circuitry to describe what's going on.

-- 
Darren New, San Diego CA, USA (PST)
   How come I never get only one kudo?

Post a reply to this message

Am 18.09.2011 18:11, schrieb Darren New:

>> Well, was thinking more about the reception of the direct input from the
>> rods and cones, separate any other processing. Sort of a..."is the
>> colour I
>> see as 'blue' the same colour you see as 'blue'?"
>
> The different rods are definitely responding to different wavelengths.
> Whether the same wavelengths correspond to the same colors is a
> different and so-far-unanswered question. I.e., "blue" is the same
> wavelength for everyone, but "blue" is a subjective experience.

Actually there are slight variations in the wavelengths to which the 
rods react; some women even have two different receptors for red-ish 
wavelengths (in addition to the blue and green receptors), making them 
particularly good at discerning color differences (ironically their male 
children have a higher risk of being born red-green color blind).

Post a reply to this message

On 9/18/2011 9:24 AM, Warp wrote:
>    It becomes even more complicated when you consider that combinations of
> different wavelengths may look the same to the human eye, yet may have
> different physical properties (eg. when reflecting from surfaces).
>
Can get really weird in some cases. Last night I was fiddling with a new 
saber I finally got wired, with mostly only light from my computer 
display in the room. When I passed this "blue" light over a cutter I had 
the thing looked almost florescence orange (its actually high visibility 
green), an old, actually orange, gatoraid container, which I use for 
storing parts, looked dark red. Now, the later I can grasp... But the 
former seems to deny common sense about how color reflection works. 
Note, the area the two items where in got barely enough light from the 
computer to "see" them, weakly, so, how the hell do you get bright 
orange out of yellow-green, when using a blue light? o.O

Post a reply to this message

Am 19.09.2011 00:14, schrieb Patrick Elliott:
> On 9/18/2011 9:24 AM, Warp wrote:
>> It becomes even more complicated when you consider that combinations of
>> different wavelengths may look the same to the human eye, yet may have
>> different physical properties (eg. when reflecting from surfaces).
>>
> Can get really weird in some cases. Last night I was fiddling with a new
> saber I finally got wired, with mostly only light from my computer
> display in the room. When I passed this "blue" light over a cutter I had
> the thing looked almost florescence orange (its actually high visibility
> green), an old, actually orange, gatoraid container, which I use for
> storing parts, looked dark red. Now, the later I can grasp... But the
> former seems to deny common sense about how color reflection works.
> Note, the area the two items where in got barely enough light from the
> computer to "see" them, weakly, so, how the hell do you get bright
> orange out of yellow-green, when using a blue light? o.O

My best guess would be that the blue light source also emitted UV light, 
and that the "high visibility green" actually is some "neon" color as 
common with text markers, which are normally that "extra-bright" because 
they not only reflect visible light, but also actually emit visible 
light when irradiated with UV light.

Post a reply to this message

> On 9/18/2011 9:24 AM, Warp wrote:
>> It becomes even more complicated when you consider that combinations of
>> different wavelengths may look the same to the human eye, yet may have
>> different physical properties (eg. when reflecting from surfaces).
>>
> Can get really weird in some cases. Last night I was fiddling with a new
> saber I finally got wired, with mostly only light from my computer
> display in the room. When I passed this "blue" light over a cutter I had
> the thing looked almost florescence orange (its actually high visibility
> green), an old, actually orange, gatoraid container, which I use for
> storing parts, looked dark red. Now, the later I can grasp... But the
> former seems to deny common sense about how color reflection works.
> Note, the area the two items where in got barely enough light from the
> computer to "see" them, weakly, so, how the hell do you get bright
> orange out of yellow-green, when using a blue light? o.O


...the thing looked almost florescence orange... probably because it is 
actualy fluorescent orange when lighted with blue to violet and UV light.
Blue light is actualy energitic enough to cause fluorescence in several 
pigments.

That high visibility green probably absorbs a fair amount of blue. The 
blue probably is not energitic enough to cause green fluorescence, but 
enough to cause the orange one.

Post a reply to this message