Color imaging useful for Mars analysis?

News: NASA Orbiter Provides Color Views of Mars Landing Site
Candidates.
10/10/07
"Beginning this week, images will be released in color as well as
black-and-white on the camera team's Web site. The colors are false
color, not the way Mars would look to human eyes. The images are
processed to maximize color differences, a technique useful for
analyzing landscapes.
"Color data are proving very useful in interpreting geologic processes
and history on Mars," McEwen said. "The images we're releasing today
include views of some of the most interesting and compositionally
diverse areas on the planet."
....
"Color is a boon to geologists who have been trying to discriminate
different surface materials and their relation to the topography,
McEwen said. "Color clearly identifies basic material distinctions
like dust, sand or rocks, light-toned layered material, and frost or
ice," he said. Color also helps geologists correlate layers in the
Martian terrain. And scientists will be able to combine data from the
high-resolution camera and the imaging spectrometer to make detailed
maps of minerals and soil types on the planet."
http://www.jpl.nasa.gov/news/news-pr...lease=2007-116

This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.


Bob Clark

On a sunny day (Sat, 13 Oct 2007 15:48:10 -0700) it happened Robert Clark
wrote in
. com:


This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.


Bob Clark

I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

Clearly also false color images provide an extra dimension that
can show some parameter of the landscape.

But we are used to watching in color.
There is the endless 'variation' or 'discussion' about
what mars would look like to us if we were standing there.

The human eye does very much of an auto white balance, we
do not perceive a white shirt very different outside in the sun
or inside with different color temperature light, we get 'used' to
the different light.
So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.

Now what can it show? Lets look at ESA Reull Vallis:
http://sci.esa.int/science-e/www/obj...objectid=34508
Actually this is supposed to be a true color picture (whatever white balance
was used, and whatever primary colors were used, was discussed in sci.astro a
long time ago, along with technical details of the camera).

But when I enlarge this, MORE is shown:
http://panteltje.com/panteltje/space...lake2color.jpg
Note the green and blue, and the green surrounding the blue.
*Could* that be water (frozen?) with vegetation?
Remember the Russians found chlorophyll in the mars spectrum?
So let's zoom in a bit closer:
http://panteltje.com/panteltje/space...olordetail.jpg
Personally I would like a closer up of that place :-)

OK, maybe you do not believe for religious reasons in life on mars,
so look here then:
http://panteltje.com/panteltje/space...ills-bunny.jpg

First we were not at the centre of the universe,
then we were not the only life form,
now we are found to have no free will,

But we can see color!

On Oct 14, 6:39 am, Jan Panteltje wrote:
On a sunny day (Sat, 13 Oct 2007 15:48:10 -0700) it happened Robert Clark
wrote in
. com:



This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.

Bob Clark

I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

Clearly also false color images provide an extra dimension that
can show some parameter of the landscape.

But we are used to watching in color.
There is the endless 'variation' or 'discussion' about
what mars would look like to us if we were standing there.

The human eye does very much of an auto white balance, we
do not perceive a white shirt very different outside in the sun
or inside with different color temperature light, we get 'used' to
the different light.
So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.

Now what can it show? Lets look at ESA Reull Vallis:
http://sci.esa.int/science-e/www/obj...objectid=34508
Actually this is supposed to be a true color picture (whatever white balance
was used, and whatever primary colors were used, was discussed in sci.astro a
long time ago, along with technical details of the camera).

But when I enlarge this, MORE is shown:
http://panteltje.com/panteltje/space...lake2color.jpg
Note the green and blue, and the green surrounding the blue.
*Could* that be water (frozen?) with vegetation?
Remember the Russians found chlorophyll in the mars spectrum?
So let's zoom in a bit closer:
http://panteltje.com/panteltje/space...olordetail.jpg
Personally I would like a closer up of that place :-)

OK, maybe you do not believe for religious reasons in life on mars,
so look here then:
http://panteltje.com/panteltje/space...ills-bunny.jpg

First we were not at the centre of the universe,
then we were not the only life form,
now we are found to have no free will,

But we can see color!

Another great place to check in color would be Valles Marineris.
There was this great color picture taken by Mars Express:

http://sciforums.com/attachment.php?attachmentid=3999

Based on Viking images it had earlier been concluded that regions of
high color variability could be due to past liquid water interaction.
One such region was Reull Vallis as you noted:

Newsgroups: alt.sci.planetary, sci.space.history, sci.astro,
sci.astro.amateur, sci.geo.geology
From: (Robert Clark)
Date: 28 Jul 2002 00:58:40 -0700
Local: Sun, Jul 28 2002 3:58 am
Subject: Liquid water on Mars and regions of high color variability.
http://groups.google.com/group/sci.a...d152929642e500


Bob Clark

On a sunny day (Sun, 14 Oct 2007 08:01:02 -0700) it happened Robert Clark
wrote in
.com:

Now what can it show? Lets look at ESA Reull Vallis:
http://sci.esa.int/science-e/www/obj...objectid=34508
Actually this is supposed to be a true color picture (whatever white balance
was used, and whatever primary colors were used, was discussed in sci.astro a
long time ago, along with technical details of the camera).

But when I enlarge this, MORE is shown:
http://panteltje.com/panteltje/space...lake2color.jpg
Note the green and blue, and the green surrounding the blue.
*Could* that be water (frozen?) with vegetation?
Remember the Russians found chlorophyll in the mars spectrum?
So let's zoom in a bit closer:
http://panteltje.com/panteltje/space...olordetail.jpg
Personally I would like a closer up of that place :-)

OK, maybe you do not believe for religious reasons in life on mars,
so look here then:
http://panteltje.com/panteltje/space...ills-bunny.jpg

First we were not at the centre of the universe,
then we were not the only life form,
now we are found to have no free will,

But we can see color!

Another great place to check in color would be Valles Marineris.
There was this great color picture taken by Mars Express:

http://sciforums.com/attachment.php?attachmentid=3999

Based on Viking images it had earlier been concluded that regions of
high color variability could be due to past liquid water interaction.
One such region was Reull Vallis as you noted:

Newsgroups: alt.sci.planetary, sci.space.history, sci.astro,
sci.astro.amateur, sci.geo.geology
From: (Robert Clark)
Date: 28 Jul 2002 00:58:40 -0700
Local: Sun, Jul 28 2002 3:58 am
Subject: Liquid water on Mars and regions of high color variability.
http://groups.google.com/group/sci.a...d152929642e500


Bob Clark

I am looking through those things, nice pdf about Pathfinder :-)
When we look a bit more into the past, to the Viking mission,
you can really learn about color calibration on Dr. Levin's site:
http://mars.spherix.com/mars.html
There are many papers, and, as you probably know, he observed seasonal changes
in the color of some stones, (I actually have this picture on the wall at home),
those changes *could* be an indication of some life growing on those stones,
using energy from the sunlight.
That, together with his life detection experiment that was positive, makes
a strong case for some form of life on mars.

I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

My disappointment with ESA is they takes months to years to release
data.
NASA puts theirs on the web within 48 hours.
Now if they only implemtent the best of each others policies ....

Jan Panteltje wrote:
On a sunny day (Sat, 13 Oct 2007 15:48:10 -0700) it happened Robert Clark
wrote in
. com:

This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.


Bob Clark

I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

Clearly also false color images provide an extra dimension that
can show some parameter of the landscape.

But we are used to watching in color.

Then you are under the age of 40. I am over that age, and we did not get
color photographs until I was about 10, and color TV until I was in high
school. Having grown up on grayscale still and moving images, perhaps
those of us in that age range don't need the color so much. Actually, a
grayscale image can be much sharper and show more gradations without
unneeded distraction, in terms of looking at aerial photos.


So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.

I disagree. If you go outside some night when Mars is in the sky, you
can find it very easily because it is the most reddish point of light in
that area (unless it happens to be near Antares in Scorpio.)

But we can see color!

Another thing: individual humans see color very differently, and some
are colorblind-- that is: their color perceptions are shifted from
spectral color, or don't exist at all. Once my dad got a color enlarger
for our darkroom and he started printing color images (usually
slide-Cibachromes) he and my mother would have endless arguments over
the shade of yellow of a dress, or the true color of a flower. The
problem wasn't equipment-- it was that they didn't see the same absolute
colors looking at the same image. Red-green colorblindness is pretty
common, but anyone with vision can distinguish shades of gray.

On a sunny day (Sun, 14 Oct 2007 12:22:03 -0500) it happened Jo Schaper
wrote in
:

Jan Panteltje wrote:
On a sunny day (Sat, 13 Oct 2007 15:48:10 -0700) it happened Robert Clark
wrote in
. com:

This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.


Bob Clark

I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

Clearly also false color images provide an extra dimension that
can show some parameter of the landscape.

But we are used to watching in color.

Then you are under the age of 40.

Wrong, I am way over 60 :-)

I am over that age, and we did not get
color photographs until I was about 10, and color TV until I was in high
school.

Highly irrelevant, but actually I worked in TV a large part of my
life, and since 1967 we had color here.
You must be aware that many painters used color all the way back to the ancient times.


Having grown up on grayscale still and moving images, perhaps
those of us in that age range don't need the color so much.

mm, never went to see a movie? Even Elvis was in color ;-)
And he's been dead for a long time.



Actually, a
grayscale image can be much sharper and show more gradations without
unneeded distraction, in terms of looking at aerial photos.

This is rubbish.
Sure, on YUV processing color resolution is limited, but not likely
in your LCD monitor, it has as many red, as green, and blue pixels.
When the image is processed as RGB there is no resolution loss.


So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.

I disagree. If you go outside some night when Mars is in the sky,

Because your eyes are adapted to earth light / earth atmosphere.
And mars is not ALL red, there are large grey and even green areas.

If you were on mars some time, I'd think your eyes would adapt.

you
can find it very easily because it is the most reddish point of light in
that area (unless it happens to be near Antares in Scorpio.)

I suggest you look up 'Color Calibration of the Martian Images' at
http://mars.spherix.com/5555-29.PDF
and go to page 12, the right side pictu
Now all of the sudden sky is blue on mars, and you see some green.



But we can see color!

Another thing: individual humans see color very differently, and some
are colorblind--

I would make no sense to include the visually disabled in a discussion about mars colors.

that is: their color perceptions are shifted from
spectral color, or don't exist at all. Once my dad got a color enlarger
for our darkroom and he started printing color images (usually
slide-Cibachromes) he and my mother would have endless arguments over
the shade of yellow of a dress, or the true color of a flower. The
problem wasn't equipment-- it was that they didn't see the same absolute
colors looking at the same image. Red-green colorblindness is pretty
common, but anyone with vision can distinguish shades of gray.

I have a lot of experience with color encoding, codecs, standards, and cameras.
Yes, you can see the smallest differences.
But also, because our eyes do the auto white trick, they adapt.

I myself have some trouble choosing a nice shirt color with artificial lights
in a shop. It is simply different from outside in the sun.
In color photography things were a lot more vague (especially if you have your
holiday pictures done at some lab) as it depends 100% on the guy processing
in some cases.
In electronic processing we can do 10 decimals accuracy if need be.
And get 100% the same result every time.
Old 'technicolor' movies looked really nice, saturates reds etc... :-)

There is an other issue with color too, we seem to be very very sensitive to
the call it perhaps 'emotional' or 'feeling' of the color.
Sometimes just a 2 point of 255 bit of color can make the color nice, or unpleasant,
to look at.
Is there an absolute color scale? Like musical notes?
Probably :-)
But like music, not everybody has a feel for that.

So, but that is an other aspect.

On a sunny day (Sun, 14 Oct 2007 16:45:18 -0000) it happened rick++
wrote in
. com:


I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

My disappointment with ESA is they takes months to years to release
data.
NASA puts theirs on the web within 48 hours.
Now if they only implemtent the best of each others policies ....

Well NASA tells us almost daily what the rovers do, but never the analysis.
So I stopped reading about: 'and now it moved to rock xxx and drilled it',
because I want to know what it found , not what it did.
There is indeed a year or so (or more?) delay until you get some scientific
papers with detail (if any) of what was found.
I really think the public already said goodbye after drilling the tenth stone!
What the public wants is aliens and lifeforms and results.
And the public funds NASA.
ESA does their best too, but has some less obvious publicity in sci.astro.
Still we get Cassini reports every day:-)

Jan Panteltje wrote:
On a sunny day (Sun, 14 Oct 2007 12:22:03 -0500) it happened Jo Schaper
wrote in
:

Jan Panteltje wrote:
On a sunny day (Sat, 13 Oct 2007 15:48:10 -0700) it happened Robert Clark
wrote in
. com:

This report is on false-color images to be released where color
differences are exaggerated. But McEwens phrasing suggests he means
his comments as a general statement about color imaging.


Bob Clark
I have always been disappointed with the BW pictures send back by NASA.
ESA got it right first time, with beautiful color images, 3D too,
and TRUE color images on top of that.

Clearly also false color images provide an extra dimension that
can show some parameter of the landscape.

But we are used to watching in color.
Then you are under the age of 40.

Wrong, I am way over 60 :-)

I am over that age, and we did not get
color photographs until I was about 10, and color TV until I was in high
school.

Highly irrelevant, but actually I worked in TV a large part of my
life, and since 1967 we had color here.
You must be aware that many painters used color all the way back to the ancient times.


Having grown up on grayscale still and moving images, perhaps
those of us in that age range don't need the color so much.

mm, never went to see a movie? Even Elvis was in color ;-)
And he's been dead for a long time.

As a matter of fact, I never saw "The Wizard of Oz" --first Technicolor
movie for wide distribution-- in color until I was about 15 years old,
and the grayscale opening confused me.





Actually, a
grayscale image can be much sharper and show more gradations without
unneeded distraction, in terms of looking at aerial photos.

This is rubbish.
Sure, on YUV processing color resolution is limited, but not likely
in your LCD monitor, it has as many red, as green, and blue pixels.
When the image is processed as RGB there is no resolution loss.

Not true. There are many RGB colors which have no CYMK or Pantone
analogs. And vice versa between the three systems. RGB is an easy, but
not very good system-- if such were the case, there would be no need for
color monitor calibration.


So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.
I disagree. If you go outside some night when Mars is in the sky,

Because your eyes are adapted to earth light / earth atmosphere.
And mars is not ALL red, there are large grey and even green areas.

If you were on mars some time, I'd think your eyes would adapt.

I seriously doubt it.


you
can find it very easily because it is the most reddish point of light in
that area (unless it happens to be near Antares in Scorpio.)

I suggest you look up 'Color Calibration of the Martian Images' at
http://mars.spherix.com/5555-29.PDF
and go to page 12, the right side pictu
Now all of the sudden sky is blue on mars, and you see some green.

Yep. Those are the false color images, not the reverse.


But we can see color!
Another thing: individual humans see color very differently, and some
are colorblind--

I would make no sense to include the visually disabled in a discussion about mars colors.

that is: their color perceptions are shifted from
spectral color, or don't exist at all. Once my dad got a color enlarger
for our darkroom and he started printing color images (usually
slide-Cibachromes) he and my mother would have endless arguments over
the shade of yellow of a dress, or the true color of a flower. The
problem wasn't equipment-- it was that they didn't see the same absolute
colors looking at the same image. Red-green colorblindness is pretty
common, but anyone with vision can distinguish shades of gray.

Neither of my parents were colorblind. But neither did they see the same
color. The same is true of my husband and I-- it's rather useless to
describe to him a color, because what I see as blue, he sees as teal,
what I see as orange, he calls dark yellow...etc. We're not trying to be
difficult. Also, various cultures don't distinguish the same
colors...which is something I find interesting. There are a number of
cultures where either blue or green doesn't exist, but they call those
two colors by the same name.



I have a lot of experience with color encoding, codecs, standards, and cameras.
Yes, you can see the smallest differences.
But also, because our eyes do the auto white trick, they adapt.

See, my eyes don't do the 'auto white trick' if I understand what you
mean. I spend a fair amount of time in caves,(zero light) and do cave
photography. Even leaving the camera out of it, carbide (flame) lighting
is heavily yellow/orange, incandescent light is white/bright light
yellow into light orange (closest to the color of the outside lit by the
sun IMO). Caves lit by fluorescent light are shifted way blue-- walls
and mud which are red orange in incandescent light look a dull
gray-brown. LED lighting depends upon which wavelength LED is being
used-- many LEDs which are nominally white are actually light yellow or
light blue. Because both fluorescent and LED light waves are squarish
waves with a short spread of wavelengths, they tend to physically hurt
my eyes. Cavers still use magnesium flash powder and flashbulbs on
occasion, even with digital cameras. Compensation has to be made if one
has blue coated flashbulbs-- the easiest kind to find at flea markets.

The point is: though all these light sources are nominally 'white' -- I
do see the actual colors of light and their reflected effects on the
surroundings. It's fairly obvious that digital cameras do too-- most
point and shoot cave photos done in a lightless cave come out ok, but
those shot in a commercial cave with incandescent lighting look like it
was taken just outside the gates of hell, as the photos are very greatly
shifted towards the yellow/red.

The earth's atmosphere appears blue only because the sun's light
reflects/refracts blue. Since Mars has a much thinner atmosphere
(approximately 1/100 that of earth) and has a much different composition
(extremely high CO2) it makes no sense whatsoever for it to have a blue
sky, or anything but a reddish/gray/sage color green (if you call that
green). I never said Mars was entirely bright red -- it sort of looks
like New Mexico desert in the Nugget or Navaho sandstone with red
residuum to me. But I don't buy blue sky and green ground.



I myself have some trouble choosing a nice shirt color with artificial lights
in a shop. It is simply different from outside in the sun.
In color photography things were a lot more vague (especially if you have your
holiday pictures done at some lab) as it depends 100% on the guy processing
in some cases.
In electronic processing we can do 10 decimals accuracy if need be.
And get 100% the same result every time.
Old 'technicolor' movies looked really nice, saturates reds etc... :-)

Your opinion. When I was shooting a lot of color print film, it was
really obvious that Fuji film was slanted towards blue/green saturation,
and Kodak towards red (to put rosy cheeks in white people's faces.)
Konica film actually was a bit slanted towards yellow, which tended to
give brighter whites. I actually hate technicolor, saturated reds, and
in film shoot and shot Fuji and Extachrome, rather than
Kodacolor/Kodachrome. Kodak Elite Chrome isn't too badly shifted to the
red, but it isn't as cool as I would like.


There is an other issue with color too, we seem to be very very sensitive to
the call it perhaps 'emotional' or 'feeling' of the color.
Sometimes just a 2 point of 255 bit of color can make the color nice, or unpleasant,
to look at.
Is there an absolute color scale? Like musical notes?
Probably :-)
But like music, not everybody has a feel for that.

Actually there is, since any color can be codified in terms of
electromagnetic wavelength.

On a sunny day (Sun, 14 Oct 2007 18:06:20 -0500) it happened Jo Schaper
wrote in
:

A very long post, I will try to address some points....

mm, never went to see a movie? Even Elvis was in color ;-)
And he's been dead for a long time.

As a matter of fact, I never saw "The Wizard of Oz" --first Technicolor
movie for wide distribution-- in color until I was about 15 years old,
and the grayscale opening confused me.

I vaguely remember going with my parents to a movie, dunno
what it was 'alice in wonderland?", in color.
And that was a cartoon.
In the fifties.
http://en.wikipedia.org/wiki/Alice_i...281951_film%29
1951!


Actually, a
grayscale image can be much sharper and show more gradations without
unneeded distraction, in terms of looking at aerial photos.

This is rubbish.
Sure, on YUV processing color resolution is limited, but not likely
in your LCD monitor, it has as many red, as green, and blue pixels.
When the image is processed as RGB there is no resolution loss.

Not true. There are many RGB colors which have no CYMK or Pantone
analogs. And vice versa between the three systems. RGB is an easy, but
not very good system-- if such were the case, there would be no need for
color monitor calibration.

Here I suppose you know little about colormetrics and color TV...
We have 3 x 12 bit RGB or even more if need be.
The issue is: Where do you put your primary colors.
There is such a thing as a color triangle, and to be able to show _all_
possible colors, this needs to be engulfed as much as possible.
In TV there are standard definitions for the primaries, and the many
encoding systems, sometimes with very small differences between them..
There is the rare earth used in CRT display tubes, the kind of backlight in
LCD displays from fluorescent tubes, now moving to LEDs, the LEDs giving
a wider display color spectrum.

None of these systems 'reproduce' the full original spectrum, just 3 basic colors
red, green, and blue, that activate the color receptors for red green and blue in our eyes.
The sensitivity curves of these receptors (averaged over many people) is
not the same as the color sensors in the cameras, sometimes the color sensor filters are not
the same as in the display device, so all is approximation.
RGB is a fine system, if you know something better there is money to be made!





So I think all the reddish mars pictures will NOT be the way we will
see things once we are actually there.
I disagree. If you go outside some night when Mars is in the sky,

Because your eyes are adapted to earth light / earth atmosphere.
And mars is not ALL red, there are large grey and even green areas.

If you were on mars some time, I'd think your eyes would adapt.

I seriously doubt it.

Our eyes adapt rather quickly.
As I pointed out, the shirt that looks white outside in the sun, ALSO
is perceived as white after you have been inside for a while with artificial light,
light of different color temperature, the 'auto white; is a system
that cameras use for example, you shoot a white object, and set the gain for
R, G, and B so these produce exactly the same amplitude (electronically).
These relative gains differ a lot for sunlight, Edison type bulbs, fluorescent light,
completely depends on the color temperature of the scene.
The brain does it automatically.




you
can find it very easily because it is the most reddish point of light in
that area (unless it happens to be near Antares in Scorpio.)

I suggest you look up 'Color Calibration of the Martian Images' at
http://mars.spherix.com/5555-29.PDF
and go to page 12, the right side pictu
Now all of the sudden sky is blue on mars, and you see some green.

Yep. Those are the false color images, not the reverse.

If you want to be pedantic then _any_ image is a false color image.
All that is happening is a change in the relative gain [amplitudes] of R, G, B.


Neither of my parents were colorblind. But neither did they see the same
color. The same is true of my husband and I-- it's rather useless to
describe to him a color, because what I see as blue, he sees as teal,
what I see as orange, he calls dark yellow...etc. We're not trying to be
difficult. Also, various cultures don't distinguish the same
colors...which is something I find interesting. There are a number of
cultures where either blue or green doesn't exist, but they call those
two colors by the same name.

mm, well, any references?


I have a lot of experience with color encoding, codecs, standards, and cameras.
Yes, you can see the smallest differences.
But also, because our eyes do the auto white trick, they adapt.

See, my eyes don't do the 'auto white trick' if I understand what you
mean. I spend a fair amount of time in caves,(zero light) and do cave
photography. Even leaving the camera out of it, carbide (flame) lighting
is heavily yellow/orange, incandescent light is white/bright light
yellow into light orange (closest to the color of the outside lit by the
sun IMO). Caves lit by fluorescent light are shifted way blue-- walls
and mud which are red orange in incandescent light look a dull
gray-brown. LED lighting depends upon which wavelength LED is being
used-- many LEDs which are nominally white are actually light yellow or
light blue. Because both fluorescent and LED light waves are squarish
waves with a short spread of wavelengths, they tend to physically hurt
my eyes. Cavers still use magnesium flash powder and flashbulbs on
occasion, even with digital cameras. Compensation has to be made if one
has blue coated flashbulbs-- the easiest kind to find at flea markets.

The point is: though all these light sources are nominally 'white' -- I
do see the actual colors of light and their reflected effects on the
surroundings. It's fairly obvious that digital cameras do too-- most
point and shoot cave photos done in a lightless cave come out ok, but
those shot in a commercial cave with incandescent lighting look like it
was taken just outside the gates of hell, as the photos are very greatly
shifted towards the yellow/red.

Because you never did a true white balance???????
The song:
You can get any color you want in the digital restaurant.


The earth's atmosphere appears blue only because the sun's light
reflects/refracts blue. Since Mars has a much thinner atmosphere
(approximately 1/100 that of earth) and has a much different composition
(extremely high CO2) it makes no sense whatsoever for it to have a blue
sky, or anything but a reddish/gray/sage color green (if you call that
green). I never said Mars was entirely bright red -- it sort of looks
like New Mexico desert in the Nugget or Navaho sandstone with red
residuum to me. But I don't buy blue sky and green ground.

Well, we will have to wait until we can buy the cheap 3 week holidays on
mars to see if the eyes adapt.
I have the feeling that those holidays will not happen in my lifetime.
But maybe the Chinese have more feeling for space adventure then the US
in the last 30 years, and will offer those trips for really low prices.


I myself have some trouble choosing a nice shirt color with artificial lights
in a shop. It is simply different from outside in the sun.
In color photography things were a lot more vague (especially if you have your
holiday pictures done at some lab) as it depends 100% on the guy processing
in some cases.
In electronic processing we can do 10 decimals accuracy if need be.
And get 100% the same result every time.
Old 'technicolor' movies looked really nice, saturates reds etc... :-)

Your opinion. When I was shooting a lot of color print film, it was
really obvious that Fuji film was slanted towards blue/green saturation,
and Kodak towards red (to put rosy cheeks in white people's faces.)
Konica film actually was a bit slanted towards yellow, which tended to
give brighter whites. I actually hate technicolor, saturated reds, and
in film shoot and shot Fuji and Extachrome, rather than
Kodacolor/Kodachrome. Kodak Elite Chrome isn't too badly shifted to the
red, but it isn't as cool as I would like.

Well I painted my old motorcycle in technicolor deep RED.
It looked really nice.




There is an other issue with color too, we seem to be very very sensitive to
the call it perhaps 'emotional' or 'feeling' of the color.
Sometimes just a 2 point of 255 bit of color can make the color nice, or unpleasant,
to look at.
Is there an absolute color scale? Like musical notes?
Probably :-)
But like music, not everybody has a feel for that.

Actually there is, since any color can be codified in terms of
electromagnetic wavelength.

Yes, now to work out those scales.....
There is the absolute, (frequency), and in the case of the way we process
the relative amplitudes of the color components we use.

One problem with color perception is that we have so many different light
types with so many spectral components, then different components we actually look at
and their sensitivity curve...
But as a relative number between R,G,B we specify most colors.
http://cubit.sandia.gov/help-version...ws_Colors.html

Mathematical relationships between several color systems:
http://www.easyrgb.com/math.php