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  1. #1
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    Ambient Lighting and Colour Temperature

    Well, amidst the drama this past week, I bring more questions. Hopefully this is the right time to do so, however. This time, it pertains to the secondary light sources.

    a) If ambience is the global lighting in a region, does that mean its strength is ultimately determined by the strength of the main lighting and any secondary light sources bouncing off a billion surfaces in an area? Does the amount of light/mid/dark values occupying a picture space indicate the level of ambience?

    b) How do people determine the hue of an ambient light? This is also tied into the question of where ambient lighting comes from. If a picture is predominantly a certain hue, can we automatically assume the ambience is that certain hue? I ask of this because the definition of ambience implies it's just light bouncing off a billion surfaces until it hits every plane. If it bounces off a billion things, what will the resulting hue be anyways?

    c) Not really ambience, but if the sky shoots down light at many many angles, can we assume any plane that remotely faces upwards will have a sky specular highlight (though some of the upward planes will reflect more than others)? This is, of course, not including other objects causing "disruption" or stronger light sources shrouding those areas.

    I hope these are worthwhile questions to ask and hopefully the questions will help people, more than just me.

    Thank you in advance.
    Last edited by Alex Chow; December 21st, 2009 at 07:44 PM.


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  4. #2
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    a) Ambient light is based on the strength of the primary light source in an area. Anything that has light falling on it becomes a source of light itself taking some of the energy depending on its surface qualities.

    b)Ambient lights hue is a product of local color of objects in the light and the strength of the primary light. Ambient light must be dependant on the airquality and strength and color of the primary lightsource combined with local color of other objects in the light. You can prove this by placing two objects in full light one in front of the other; if the first object has a local color, or the primary light has a strong local color, it will alter the color of the shadow of the second object. In space there is no ambient light because there is no atmosphere.
    c) When outdoors the primary lightsource is the sun and the secondary source of light is the sky itself. When there is no direct primary light falling outside, (think of a cloudy day or forest canopy) the specular highlights on an object come from the sky if nothing occludes it from the object.

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    nice to see a good question with a really good response especially what with all the hoo-ha.

    I've been thinking about this lately too.

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    Isn't the sky too diffuse to have a specular highlight?
    Although my confusion might have to do with not specifically understanding
    the word specular.

    edit: OK I got it confused. Whether the object has a specular highlight or not is
    pretty much dependant on its reflective qualities instead.

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    I think specular surfaces wil show specularity but not in a hotspot like fashion as the light is hitting it from all angles and therefore bounces into our view at all angles. If you have a strong light source such as the sun you will see a clear specular highlight. Otherwise it would change the temperature and value mostly.
    Ofcourse, it also depends on the amount of specularity and the smoothness of the surface.

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  12. #6
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    AC


    a) Yes

    b) Yes

    c) Yes, also the further the subject moves away from the highlight the truer the color till it reaches shadow. In the shadow the ambient light will reflect and the color reflection is the color you use.


    I hope that clears things up, Bruce

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  14. #7
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    The color and strength of the same ambient light will appear different under different conditions with a primary light, this is why direct observation is so important for how you approach painting it; most artists overpaint the secondary and tertiary light sources. This is a function of your eyes ability to adjust to conditions. If you move from a bright office or daylight setting to a dark basement there is a period of adjustment for your eyes but the rooms lighting hasn't really changed.
    When painting, the longer you stare at a dark area in the shadows or a bright area in the light the more you will see in those areas. The tendency is too overpaint the value and color separations as an isolated passage, but doing so undermines the sense of light for the whole painting. This is why it is important when painting to keep the big divisions of light and shadow in your painting relative to each other and the details are added to those areas without replacing the initial comparisons.

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    Quote Originally Posted by dpaint View Post
    The color and strength of the same ambient light will appear different under different conditions with a primary light, this is why direct observation is so important for how you approach painting it; most artists overpaint the secondary and tertiary light sources. This is a function of your eyes ability to adjust to conditions. If you move from a bright office or daylight setting to a dark basement there is a period of adjustment for your eyes but the rooms lighting hasn't really changed.
    When painting, the longer you stare at a dark area in the shadows or a bright area in the light the more you will see in those areas. The tendency is too overpaint the value and color separations as an isolated passage, but doing so undermines the sense of light for the whole painting. This is why it is important when painting to keep the big divisions of light and shadow in your painting relative to each other and the details are added to those areas without replacing the initial comparisons.
    Quoted for emphasis. This is SOOOOOOOOO important.

    Tristan Elwell
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  17. #9
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    I think I often paint secondary and ambient lighting too weak. :/ Does that statement imply that the secondary/tetiary lighting is often painted too strongly or weakly? Both?

    dpaint, do you mean that it's better to paint the light/dark relationships before the eye adjusts or after?

    This thread has been great so far! Thank you!

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    For realism you want the initial idea of relative strength between light and shadow, this, more than anything describes the quality of light to the viewer. all other information must conform to these broad masses of color and value or you weaken the affect. Most people exagerate the fill lights, not de-emphasize them.
    Anything can be manipulated for style and emphasis but everything must be considered when you deviate from the norm, otherwise you fracture the painting.

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  20. #11
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    Can I get an AMEN?! Halleluja Bruthah! That's why painting/studying from life is so important...but I'm just preachin to the choir so...great thread!

  21. #12
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    This thread has been great Thanks everyone!

    But one more quick question

    From multiple sources, I'm told white is inherently a cool colour. How true is this? In Alla Prima by Richard Schmid, it implies ANY hue gets cooler (and lighter obviously) when mixed with white. For warm colours, I have no problems with it. I find this hard to believe when it applies to cool colours; how is a blue mixed with white cooler than a saturated blue?

    I'm beginning to play with very subtle temperature shifts and something like this may hurt me in the end.

    Thanks.

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    Quote Originally Posted by Alex Chow View Post
    This thread has been great Thanks everyone!

    But one more quick question

    From multiple sources, I'm told white is inherently a cool colour. How true is this? In Alla Prima by Richard Schmid, it implies ANY hue gets cooler (and lighter obviously) when mixed with white. For warm colours, I have no problems with it. I find this hard to believe when it applies to cool colours; how is a blue mixed with white cooler than a saturated blue?

    I'm beginning to play with very subtle temperature shifts and something like this may hurt me in the end.

    Thanks.
    yes awesome thread indeed!
    to your question, blue mixed with white gets more violet. I know this from digital art experience. Not sure about traditional but as far as I can tell, there's subtle change in temperature when you mix blue with white towards cooler.

  23. #14
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    Alex, are you working digitally or traditionally? The cooling effect of white is far more of an issue when dealing with actual paint (it has to do with the physics of pigments), and, on top of that, varies among different whites. In other words, titanium, zinc, and lead whites all shift tints slightly differently.

    Tristan Elwell
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  24. #15
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    Quote Originally Posted by Elwell View Post
    Alex, are you working digitally or traditionally? The cooling effect of white is far more of an issue when dealing with actual paint (it has to do with the physics of pigments), and, on top of that, varies among different whites. In other words, titanium, zinc, and lead whites all shift tints slightly differently.
    I work both digitally and traditionally. I use Zinc White when I paint with gouache.

    I'm not so much concerned about the mixing consequences. My main concern is that if the addition of white truly does cool all hues down, it may explain why I'm screwing up temperature situations, especially when I'm establishing a cool light/warm shadow setting. I found it hard to believe when Schmid stated how cool hues with white look more cool than the saturated versions of those hues. My painting instructor also stated this before.

    I must be blind because I don't see how this can be true :/ . I was sure that white simply "neutralizes" in that it will cause warms to feel cooler and cools to feel warmer.

    EDIT: I think "feel" is a better word to describe this situation.
    Last edited by Alex Chow; December 19th, 2009 at 06:36 PM.

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