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Thread: All Day Long "Fire Light".

  1. #1
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    All Day Long "Fire Light".

    All you weather phenomena fans I have a riddle.

    Huge brush fires timed with a still air mass had ashes from a fire 93 miles to the north of my location raining down on us for two days. The smoke was overcast thick, though fortunately at a good altitude.

    My question is, when the sun was high in the sky and you were standing in full sunlight the light looked "normal-ish" BUT, (and it's a big but), when you stood in the shade, like under a balcony or from indoors looking through an open doorway, the scenery looked sunset red!

    Is there a reason for this or is this too subjective to answer properly?
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  2. #2
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    Can you clarify?

    You're standing in the bright sun and the landscape looks normal, you walk into some shade and the same landscape looks reddish?

    Is there a time delay in there? Either for change in sun or change in your pupils or change in your brain interpreting neutral white?

  3. #3
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    Quote Originally Posted by DaveC426913 View Post
    Can you clarify?

    You're standing in the bright sun and the landscape looks normal, you walk into some shade and the same landscape looks reddish?

    Is there a time delay in there? Either for change in sun or change in your pupils or change in your brain interpreting neutral white?
    Ah! Pupils!

    I forgot about them! Yeah, there was definitely enough time for a pupil change. And I have good reaction time on them too. I take a tsp of cod liver oil daily. (Mainly because I notice when I don't! )

    Still, it was a striking effect!
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  4. #4
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    My money would be on the brain recalibrating its white balance.

    When you're out in the sun, everything's reddish, so your brain cancels it out, and you see white.
    Moving into the shade gives you some colour contrast, and your brain now notices the red cast.

  5. #5
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    I did some experiments lighting paintings with bluish and yellowish light, same intensity 50 lux as recommended for conservation. People judged the more yellow light more evenly distributed and warmer although the perception of colours seemed the same. Because of the brain white balance calibration. The light source was from above each painting. The normal blue sky is very blue compared with normal direct sun which is yellow, as judged by the brain choosing what is “white” even with no white objects in the field. Did the high dust make the sky look normally blue or with a red sunset tinge?
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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  6. #6
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    High altitude smoke particles I would assume are small enough to scatter away more of the blue light than normal. Much redder sunsets are likely as well. The white adjusting by your retinex (color constancy) has its limits and perhaps you experienced this difference under these smokey circumstances. You might try looking at a white sheet of paper in the shade, assuming you have direct sunlight. Notice its color. Normally it will have a noticeable tint of blue, but it might not under these circumstances.
    We know time flies, we just can't see its wings.

  7. #7
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    Hi George.

    The responsible fires are still burning and the red effect is still noticeable, but much more fainter as the various winds have been blowing now.

    But I'll do that once I get out of my pajamas and actually start my day!.

    (It's just after 8 AM local.)
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  8. #8
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    Quote Originally Posted by George View Post
    Normally it will have a noticeable tint of blue...
    Compared to what?

    Seen in red light, a sheet of paper will still look bluer than its surroundings. Without an objective reference, it's still going to seem blue to his brain.

  9. #9
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    Quote Originally Posted by DaveC426913 View Post
    Compared to what?

    Seen in red light, a sheet of paper will still look bluer than its surroundings. Without an objective reference, it's still going to seem blue to his brain.
    Compared to not being in the shade. The difference was surprising to me and I noticed this difference by accident when trying to produce a nice solar spectrum with a quality prism mounted on a two-story roof.

    Direct sunlight makes white paper bright white, but in the shade the blue light from the sky upon the same paper will overcome the eye's color constancy ability to self-correct and you will see a distinct blue tint. I think it's worse if the eye can see any direct sunlight outside the shade since the brighter light becomes the eye's reference light, if I understand this process, and I might not, admittedly.

    So if extra scattering takes place, then the paper in shade will look less blue than normal, but I suppose all one needs to do is look for the sky to be diminished in blue light due to extra scattering, if this is happening.
    Last edited by George; 2018-Jul-13 at 03:02 PM.
    We know time flies, we just can't see its wings.

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