The Dimensions of Colour - a colour theory discussion thread - Page 12

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  1. #331
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    Thanks for the swift reply.

    Thats interesting to think about. definetly laid those questions to rest.

    I have another one.

    I was researching atmospheric perspective. My hunch was that it increases exponentially as the distance travels back in space.

    It has been described in places that the atmospheric particles decrease in amount exponentially the higher you get in the atmosphere.

    However i couldnt find anything relating to distance along the z axis.

    I figured it would be exponential for two reasons;

    inverse square cube law / power law

    and because of the height to amount relationship described above.

    Then i stumbled across this;

    The inverse square law mentioned in the comments doesn't really come into play here because the fall-off in light energy is exactly balanced by the reduction in apparent size of the object. (An object twice as far sends only a quarter of the light energy to the eye, but also only occupies a quarter of the visual area, so the light energy per area of the visual field is the same). -David briggs


    It was from james gurneys blog.

    Now i might be wrong, however i thought about this and thought,

    Even if the light ENERGY is 1/4, the light INTENSITY is the same due to the strength of the light? So the light that reaches our eyes would be greater than if we calculated using the energy as our benchmark.

    what do you think?



    Also: just wondering do you know if/how LRV's (light reflectance values) relate to brightness or values? Just been wondering about the connection. can a connection be made?

    Here is a study i did using a photo.

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    Last edited by Siphonophores; January 15th, 2014 at 02:33 PM.
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  3. #332
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    Quote Originally Posted by Siphonophores View Post
    The inverse square law mentioned in the comments doesn't really come into play here because the fall-off in light energy is exactly balanced by the reduction in apparent size of the object. (An object twice as far sends only a quarter of the light energy to the eye, but also only occupies a quarter of the visual area, so the light energy per area of the visual field is the same). -David briggs


    It was from james gurneys blog.

    Now i might be wrong, however i thought about this and thought,

    Even if the light ENERGY is 1/4, the light INTENSITY is the same .....
    That's exactly what I'm saying - the intensity (luminance) is the same because the smaller amount of energy is concentrated in a correspondingly smaller visual field.

    Quote Originally Posted by Siphonophores View Post
    Also: just wondering do you know if/how LRV's (light reflectance values) relate to brightness or values? Just been wondering about the connection. can a connection be made?
    Sure, it's the nonlinear luminance to lightness relationship that is given as a cube root formula for CIEL* (L = 116 (Y/Yn)1/3 - 16), so for example an L* of 75 corresponds to an LRV of about 48.
    http://www.huevaluechroma.com/081.php

    With your spheres, wouldn't you expect the shadow side to be a different hue to the light side, given that there is probably a difference in colour between the sunlight and the light from the opposite side of the sky?

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  4. #333
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    haha! Yea i think i was just confused with that. Thanks.

    Also big thanks for this post. This just gave me a Huge leap in my thinking. I was getting confused between parameters.

    Just got a few (well not so few) questions.

    I found this definition and liked it i was wondering if you thought it was right?


    standard theories of visual surface perception, for instance, posit that brightness (“perceived luminance”) and lightness (“perceived reflectance”) constitute the perceptual counterparts to the physical dimensions of luminance (light intensity physically registered by the eye) and diffuse surface reflectance (ratio of physically incident and reflected light intensity)

    http://www.journalofvision.org/content/13/1/14.full




    Also what do you think about this?

    Anchoring theory assumes that lightness is a psychological continuum that extends upwards beyond the physically
    possible reflectance range (0-1), and that high values on this continuum represent surfaces that appear to glow

    http://www.journalofvision.org/content/13/1/14.full


    Do you know about gamut relativity? What do you think about this theory?

    A key aspect of gamut relativity is the redefinition of brightness and lightness as computationally defined modes, rather than dimensions, of vision. According to this view, the brightness mode corresponds to global anchoring (λ = 1) and the lightness mode to local anchoring (λ = 0).


    Is blackness bias a principle we can use in painting? Would it apply in direct sunlight?



    ALso The information on relative brightness was a real eye opener. Is there any info about the different value steps for the different colors? or any general rules?


    hmmmm yea those spheres were a tough one. I think maybe the shadow would be a little colder due to the lessening light of the sky, but also with a slight warm band for the alpenglow.


    Here are some more Studies i was doing, Though i did them before reading this post.


    Also how would you deal with the three modes of vision in one picture? say there was a dark area then like a spotlight?

    Last edited by Siphonophores; January 19th, 2014 at 01:27 PM.
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