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Posted by Jan Panteltje on October 15, 2007, 5:06 am
Please log in for more thread options On a sunny day (Sun, 14 Oct 2007 18:06:20 -0500) it happened Jo Schaper
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_in_Wonderland_%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 picture:
>> 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-version8.1/Appendix/X-Windows_Colors.html
Mathematical relationships between several color systems:
http://www.easyrgb.com/math.php
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