Please explain

"KeithK" wrote in message
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In article ,
(Kevin Brooks) wrote:



I believe what he was referring to is the fact that red, green, and
blue are *the* primary colors.
Er, isn't that red, green, and yellow?

Actually, red, green blue are "the primary colors of light" but
red, yellow and blue serve the same purpose for pigments.

The red, green blue thing originates in the human eye. In a "normal,
healthy eye" there are four types of receptors: one type is most
sensitive in the red region of the spectrum, one in the green, one
in the blue and one (that provides night vision) is sensitive across
a the great swath of the visible spectrum up into the ultra violet.
None of the types have exactly sharp cut offs in sensitivity and in
fact the color cells have a good deal of over lap in their sensitivities.
It's because of this over lap that mixing the "primary colors" fools
the eye into seeing the infinite colors and shades that lie between.

(Regnirps) wrote in message ...
(Kevin Brooks) wrote:

If you're dealing with paint it would be red, blue and yellow (or Cyan,
Magenta and Yellow)

You are responding to the wrong poster--I did not say the above.

Brooks


RGB corresponds to the color detectors in the retina.

With paint, as in having it mixed at the hardware store, one uses a bunch of
colors, like 10 or 12 to form a polygon in the color space and give a much
larger pallet of colors. Just RGB or CMY gives a triangle and leaves out a lot
of the perceivable colors. See any chromaticity diagram (which is three
dimmensional and usually shown as two with shading for the third).

It is possible to "see" colors that do not exist in the electromagnetic
spectrum, like brown. Likewise, the orange from red+yellow is a product of the
brain and retina as opposed to an orange spectral line from a sodium lamp. They
look the same to us but a simple filter will show the difference.

So, what and NVG will react to can be auite different from what the eye alone
will react to.

Most of modern color/brain theory comes from work by Land who found ways to
"fool" the brain into seeing full color with just two colors in the projection.

Photographers talk about addititive and subtractive colors depending on whether
a process uses primary dyes or filtering gels.

But we are not dealing with paint (for which the proper selection is
the latter, IIRC). BRBR

-- Charlie Springer

The Feynmann is of course a very good reference.

"BUFDRVR" wrote in message
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Green + Red = Blue???
Mind boggles.

hmm, doesn't it?

Green is yellow + blue

"Tarver Engineering" wrote in message
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"BUFDRVR" wrote in message
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Green + Red = Blue???
Mind boggles.

hmm, doesn't it?

Green is yellow + blue



Go back to sleep, John



John

"John Mullen" wrote in message
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"Tarver Engineering" wrote in message
...

"BUFDRVR" wrote in message
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Green + Red = Blue???
Mind boggles.

hmm, doesn't it?

Green is yellow + blue

Go back to sleep, John

Actually, we make NVG repeaters for Aussie rotary wings. There is quite a
bit of extra effort required for the timing of the lighting circuit and
filtering; even with HP NVG green LED arrays.

Red is bad, green is good, but not just any green.

Regnirps wrote:

(Kevin Brooks) wrote:


If you're dealing with paint it would be red, blue and yellow (or Cyan,
Magenta and Yellow)


RGB corresponds to the color detectors in the retina.

With paint, as in having it mixed at the hardware store, one uses a bunch of
colors, like 10 or 12 to form a polygon in the color space and give a much
larger pallet of colors. Just RGB or CMY gives a triangle and leaves out a lot
of the perceivable colors. See any chromaticity diagram (which is three
dimmensional and usually shown as two with shading for the third).

Which is why painting is an art. However, pretty much every ink-jet
printer uses CMY + black. Higher quality ink-jet printers use about six
different colours.
It is possible to "see" colors that do not exist in the electromagnetic
spectrum, like brown.
Yes, brown isn't spectral colour.
Likewise, the orange from red+yellow is a product of the
brain and retina as opposed to an orange spectral line from a sodium lamp. They
look the same to us but a simple filter will show the difference.

Sure, a combination of two primaries can lead to the same sensation as a
specific spectral colour.

So, what and NVG will react to can be auite different from what the eye alone
will react to.

Most of modern color/brain theory comes from work by Land who found ways to
"fool" the brain into seeing full color with just two colors in the projection.

Photographers talk about addititive and subtractive colors depending on whether
a process uses primary dyes or filtering gels.


But we are not dealing with paint (for which the proper selection is
the latter, IIRC). BRBR


-- Charlie Springer

The Feynmann is of course a very good reference.

We're making the same point here. Different primaries can be used in
different combinations to produce the same colour sensation on your retina.

Regards,
Ralph Savelsberg

"BUFDRVR" wrote in message
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The green plus red is blue boggles my mind.

Still,

I wouldn't call myself a colour spectrum expert, but I'll give it a try:
The NVGs are most sensitive to light at the low frequency/ long
wavelength end of the visual spectrum, i.e. the red end of the spectrum
(and unlike the human eye even is sensitive to somewhat lower
frequencies in the IR range).
Green is associated with higher frequencies/smaller wavelengths than
red. A red light of a certain intensity produces a far stronger response
in the NVG than a green light of similar intensity would, since green
lies further away from the wavelength range to which the NVGs are most
susceptible. Pretty straightforward.
As for the blue, this is associated with even higher frequencies/smaller
wavelengths than the green, so it should be even less visible, which
gives no explanation whatsoever for why green would work better than
blue, unless with blue the worry would be that you wouldn't bee able to
see that at all, while wearing your NVGs.

Wow, this thread has gotten good, imagine that I'm actually learning here.
Unfortunately, I obviously misunderstood the NVG experts words, I thought
he
said blue light was closer to the red spectrum than green, but if you're
correct (as well as another poster who posted the exact frequencies for
each
color...impressive), I must have misunderstood. Anyway, he was correct, my
blue
indiglo watch washed out my NVG's, if only slightly, while the green light
of
similar intensity did not.

Green light is the best way to blind NVGs, as that is the light they are
most sensitive to. Quite a bit of care is required to produce the correct
frequency of green light, for an NVG display to be readily readable.

Green light is the best way to blind NVGs

I hope you mean red. With NVGs on, I can see a glow from a red light turned on
*behind me*. No matter how bright a green light is, it will not wash out NVGs
anymore than red light.


BUFDRVR

"Stay on the bomb run boys, I'm gonna get those bomb doors open if it harelips
everyone on Bear Creek"

BUFDRVR wrote:

Green light is the best way to blind NVGs

I hope you mean red. With NVGs on, I can see a glow from a red light turned on
*behind me*. No matter how bright a green light is, it will not wash out NVGs
anymore than red light.

nope, that's Tarver for ya.... forged in the "D-U-M-B" position.

redc1c4,
ask him about the "strakes" on the F/A 22. %-)
--
"Enlisted men are stupid, but extremely cunning and sly, and bear
considerable watching."

Army Officer's Guide