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Thread: Colour of Mars

  1. #1
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    Colour of Mars

    A person raised the question of NASA "honesty" with regard to the Viking images from 1976.

    The original images showed a blue sky, which was subsequently changed to be red.

    My understanding of this is that it had to do with the colour calibration of the camera. Even so, people associated with Viking admit that they weren't that sure if the colour was an accurate representation.

    This was apparently settled with Pathfinder, and the colour would appear to be more of a 'butterscotch' colour than red. Even so, there would seem to be professionals who still bias the colour because of doubts that the colour calibration is accurate.

    Can BA / members explain this in a little more detail (for the layman)?

  2. #2
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    Cornell University: Estimating the True Colors of Mars (from Pancam Home)

    The detailed math and computer processing that goes into this process is described in the next section. It's important to point out that this is only an estimate of the true color of each of these scenes from Mars. As mentioned above, everyone perceives color differently, and different computer monitors and printers display color differently. The colors also vary with time of day, and even from day to day because of different amounts of dust and clouds in the Mars atmosphere. And there are also sometimes small calibration problems with the images that can cause errors in the true color calculations. We've done the best job that we can to estimate the colors. Ultimately, the true test of color success will probably have to await the judgment of the real experts: the first astronauts who go there and see the place for themselves sometime in the next few decades...
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  3. #3
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    Ultimately, the true test of color success will probably have to await the judgment of the real experts: the first astronauts who go there and see the place for themselves sometime in the next few decades...
    As if that's going to work...

    Astronaut #1: It's red.

    Astronaut #2: No, it's more orangey brown.

    Astronaut #3: It's maroon you idiots.

    The simple fact is a camera can reproduce color better than a human trying to tell you what color something is.

  4. #4
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    I remember a hoagland scene in which a picture released by NASA showed a green patch on Mars. NASA later corrected the patch to a "truer gray"

    I can easily see the layman asking "if i can buy any old cheap camera and take true color photographs; Why cant NASA?"

  5. #5
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    Quote Originally Posted by Obviousman View Post
    A person raised the question of NASA "honesty" with regard to the Viking images from 1976.

    The original images showed a blue sky, which was subsequently changed to be red.

    My understanding of this is that it had to do with the colour calibration of the camera. Even so, people associated with Viking admit that they weren't that sure if the colour was an accurate representation.

    This was apparently settled with Pathfinder, and the colour would appear to be more of a 'butterscotch' colour than red. Even so, there would seem to be professionals who still bias the colour because of doubts that the colour calibration is accurate.

    Can BA / members explain this in a little more detail (for the layman)?
    The question is what is meant by “true” colour. Is it the colour the human eyes would see under Mars-sky-illuminant or under Earth-sky-illuminant (which is standardized by ISO to be D65-illuminant). Have you ever wondered about the colour of things under a sodium discharge lamp illuminant? This example should tell you everything about the meaning of “true” colour. If the Mars landers had taken Earth-daylight-lamps with them to illuminate the Martian soil we would know at least how the soil would look here on our planet.

  6. #6
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    Quote Originally Posted by Neverfly View Post
    I remember a hoagland scene in which a picture released by NASA showed a green patch on Mars. NASA later corrected the patch to a "truer gray"

    I can easily see the layman asking "if i can buy any old cheap camera and take true color photographs; Why cant NASA?"
    As I just said in my last post: It depends strongly on the illuminant. Take some Earth-daylight-illuminant with you, and you will be very happy with the colour reproduction of your cheap camera, without any doubt.

  7. #7
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    Google Image for "Colour illusions" to see how our colour perception is influenced by many things. (Use 'color' and see another set! Strange, that!)

    NASA uses colour filters to isolate different wavelengths, but each wavelenght may be perceived differently. They often use exaggerated or even false colour to display different wavelengths of light. And colour reproduction by screen or printing is a construct of primary colours anyway, that only appears natural because the eye/brain makes it so.

    JOhn

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