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Thread: The Dimensions of Colour - a colour theory discussion thread

  1. #131
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    Hi David,

    I've recently begun trying to study color on my own, and your tutorial is one of the best sources I have found so far. Thanks!

    I have a question, though... in the chapter on Hue (on the section on the traditional artist's wheel) you make a brief reference to Johannes Itten's contribution and mentions "the inexplicable popularity of Itten's books". Would you mind elaborating a bit on this?

    In addition to your tutorial (and Ron Lemen's brief tutorial posted here on CA.org), I've been working with Parramon's Color Theory book and have recently borrowed a copy of Itten's The Art of Color from the library. However, since self-studying such a complex topic is already hard enough, I want to make sure I keep on the right track... so any comments regarding the potential or fundamental problems with Itten's book would be much welcome. Thanks a lot in advance!
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  3. #132
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    S.M.

    Sorry for the long delay S.M., but (take note everyone) asking seven questions at once is just asking to be put on hold!

    1. "Tonal painting" or "tonal realist painting" refers to painting with the aim of evoking the visual appearance of the subject. I found a concise online definition here:
    http://www.chadwooters.com/ARTIST_Phases.html

    2. The uniform saturation principle simply means keeping the same kind of light from dark to light and merely increasing its brightness. It's always the underlying relationship when the eye is adapted to the general lighting levels, but it's also always modified by specular reflection of environmental light. In addition to the bounce light that you mention, specular reflection of a bright background on the receding planes would also significantly modify the colour relationships. In addition, by appropriately increasing the brightness and decreasing saturation of the lights you may be able to create the effect of very bright lighting beyond the level of adaptation of the eye.

    3. Two factors that can affect saturation relationships in photos are overexposure and consequent "clipping" of colour in the lights, and colour "noise" in shadows.

    4. Regarding the red ball, yes I think the situation you describe may result in some sort of yellowish image colour (depending on the relative strength of the components), although the perception would probably still be of a green specular reflection on a red ball.

    5. Lab vs RGB modes: Adjustment controls such as "saturation"", "brightness", and "contrast", and the various commands like "desaturate" work on different colour dimensions in the different modes. For example, the "Desaturate" command in Lab mode give you a genuine greyscale version of your image, whereas the same command in RGB mode gives you artificially distorted tonal relationships. In this particular case the Lab version is clearly preferable, but in general it's good to learn how the commands work in all the modes to equip yourself with the full range of capabilities.

    6. Human skin is translucent and allows significant subsurface light transport. I think that the saturated colour you are seeing in your photo of your hand results from light being transmitted through the skin instead of being just reflected from it.

    7. In Table 10.1 the middle row is obtained by reducing the starting value of 100 according to the inverse square law, and the bottom row is obtained by applying a 0.45 power function (see Poynton Color FAQ: 4. What is lightness?) to convert these to relative values of HSB "brightness".

    If you have any more questions I'll try to get on to them a bit quicker!
    Last edited by briggsy@ashtons; December 3rd, 2009 at 10:48 PM.
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  5. #133
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    bkkm

    The real problem with Itten is not so much what is in the book as what isn't. Itten's conception of the scope of colour theory was strongly influenced by the Farbenlehre of Goethe (1810), which was a vitriolic and spectacularly misguided attack on the scientific approach to colour vision pioneered by Newton. Itten did at least admit that Newton was right about the spectrum, but otherwise, like Goethe, he ignored almost every development in our scientific understanding of colour after Newton. For example, like Goethe, he explained afterimages in terms of eye animism (the eye "requires" the complementary and "spontaneously generates" it if it isn't already present), not mentioning the fact that these phenomena had already been (at least partly) explained in terms of changing relative sensitivities of three receptors by Thomas Young in 1807 (and even earlier by Palmer).

    A bit like Betty Edwards is for drawing, Itten might arguably be ok as a very first introduction to colour if you know nothing about the subject, but you'll want to get beyond that level as soon as possible. His simplistic eighteenth century colour wheel is ok to communicate the basic idea of the circular dimension of hue, but you'll find that it doesn't actually work for mixing colours on your computer or with your paints, and you'll need different hue circles for each of these situations. The colour sphere he adopts (originally published by Goethe's friend Runge in 1810) is a good introduction to the basic conception of three dimensions of colour forming a space, but again you'll want to go beyond it to the more sophisticated conceptions of Munsell or Arthur Pope to put the conception into practice.

    It isn't really Itten's fault, but the continued widespread use of his book as the be all and end all of colour theory, nearly fifty years after it was written, and nearer a hundred after his ideas were formulated, is connected with a widespread and powerful tradition of ignorance in art teaching that refuses to engage with any scientific understanding of colour whatsoever. The scale of this great leap backwards is emphasized when you reflect that in the early twentieth century it was an art teacher, Albert Munsell, who invented the most widely used colour order system in the world.
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  7. #134
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    I keep forgetting this thread exists!

    Hey, Briggs and other lurkers. Thanks for this thread. I never got to reading this but when I had a chance, it was truly a land of information.

    If you do not mind, I have a few questions.

    a) How do you ultimately determine the value relationship between light and shadow in a given environment? I was quite intrigued with the "ball in photo" exercises because I wouldn't know where to start with those. In fact, often my struggle comes from finding the correct contrast in a situation. Things just look out of place...

    Does it relate to "Consistency in Relative Brightness"? My current guess is that all objects in an environment (the relationship between main light and secondary light hitting the shadows) will reduce brightness by a percentage when going light to shadow, and each environment will have a different percentage.

    b) Sort of similar to question a), but relate it to saturation. It's not so much a problem in a theoretical white main light-white secondary light situation (since that retains saturation between light and shadow), but what happens in coloured illumination? Often times, I find that I overexaggerate the saturation and hue shifts in coloured illuminated environments. Are there ways to actively make sure this doesn't happen? Are there ways to make sure coloured illumination looks consistent between objects?

    c) In this post, you've stated that "In addition, by appropriately increasing the brightness and decreasing saturation of the lights you may be able to create the effect of very bright lighting beyond the level of adaptation of the eye".

    What is "appropriately"? Often when I decrease the saturation, temperature shifts along with it and, depending on the saturation of the shadows, it will also muddy up the object. Are there methods to retain temperature relationships (warm/cool, cool/warm) when decreasing saturation for this purpose?

    Thanks in advance.
    Last edited by Alex Chow; December 14th, 2009 at 12:40 PM.
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  8. #135
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    Whoa... just took a quick look at the site, and damn. Definitely thank you, very useful.
    "I have learnt silence from the talkative, toleration from the intolerant, and kindness from the unkind; yet strange, I am ungrateful to these teachers." - Kahlil Gibran


    Sketchbook: Critique greatly appreciated =)
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  9. #136
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    Dr. Briggs, This has made me realize that I know absolutely nothing about color( in terms of realistically representing an object).
    Firstly, the uniform saturation principle boggles my mind because they images with the half lights having a higher chroma do indeed look more " realistic" to me than the spheres having uniform chroma throughout. I may even be using the wrong word- from what I can decipher from your text, chroma is the extent to which a hue is farthest from grey, correct? and saturation is the purity of the hue? I have a hard time finding the difference between those definitions and I have read that page about 4 times over. Also the image you have of a painting where you attempted to create a more " realistic" sphere of her skin tone seems infinitely less realistic than what I see in the painted image.

    Also, related to this, I have always been told that the shadow will be of a complimentary color to that of the light, which you say is not true. Reading your text almost leaves me to question that I see color right at all. This may perhaps make sense, as random internet color tests have told me that I may be partially color blind. I don't really know how trust worthy these are because they diagnose that I am partially red/green color blind and I have never noticed seeing something grey, or of a different color that someone has told me it is actually different.

    If you have read all that and still don't know what I'm asking, which I would completely understand- I would like a more simple description of how light , and how progressively less light, affects the perception of a color of an object.

    The sight is very informative- if only I could wrap my head around it!
    "A drawing is not necessarily academic because it is thorough, but only because it is dead. Neither is a drawing necessarily academic because it is done in what is called a conventional style, any more than it is good because it is done in an unconventional style. The test is whether it has life and conveys genuine feeling."- Harold Speed
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  10. #137
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    Thanks for the input, The Pariano

    The whole site is in need of an update, which I'm going to start posting soon. It won't make it any simpler, but hopefully parts of it will at least be clearer. In particular I'll make it as clear as I can that, while the uniform saturation principle describes the underlying pattern, the final effect is modified by reflections of the environment, and also by the adaptation state of the eye.

    The flesh coloured sphere may not be one of my finest efforts, but even so I find it hard to see the portrait as being, say, more easily mistaken for a photograph.

    Regarding saturation vs chroma, I'm told that Figure 9.8 on this page helps:
    http://www.huevaluechroma.com/093.php

    The light in shadow zones typically does appear the complementary color to that of the main light - I'm not sure what I said that made you think I thought otherwise.

    Finally, colourblindness exists in all degrees. If the classic Isihara tests indicate a problem that otherwise goes unnoticed, then you probably have only very slightly anomalous vision. They are widely available on the internet, e.g.:
    http://colorvisiontesting.com/ishihara.htm
    http://www.premlobo.com/eyetest.swf
    More sophisticated tests have been developed more recently that pick up some deficiencies that Isihara misses, but I don't have any links offhand.


    David

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    To anyone in Sydney - I'm giving a public lecture at the Art Gallery of New South Wales this Friday 1-2 pm on "Colour and light in the work of Rupert Bunny", in connection with the Rupert Bunny exhibition. Free, all welcome - please say hi if you come along!
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  11. #138
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    This is so helpful! Thanks so much!
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  12. #139
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    I'm desperately trying to banish the amateurish "chalky" look of my paintings and your website is a boon...inasmuch as I can decipher. I haven't yet been able to posit any rational questions yet about what is perplexing me. I think I will try your spheres in photo environments exercise, I imagine that will help me see what it is that I truly don't understand. Thank you so much for the invaluable resource that is 'The Dimensions of Colour'.
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  13. #140
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    Although a tough read, the site is the best resource on colour I could find as a beginner. After re-reading things and making notes, things are starting to sink in. I don't know if you still reply to questions, but I would appreciate it if you could point out any errors in my understanding of specular/diffuse reflections:

    1. Every surface can be considered as reflecting diffuse and specular light, where the relative amount of each is dependent on the material of the surface.
    Diffuse reflection of light gives the object its form/colour, specular reflection of light is an image of a light source.

    2. Diffuse reflection of light by the environment (or any object) is a light source for another object (where that object again reflects that light both as diffuse and specular).

    3. Specular reflection results from light that is unchanged by the object and is an ADDITIVE mixture of the colour of the reflected light source and the colour of the reflected diffuse light from the specular's location (following the angle rule).

    Considering the picture below (numbers correspond to brightness levels gathered using color picker).
    The highlight is very bright, thus drowning the diffuse reflection at that location and keeping the colour of the light source.
    However the diffuse reflection of light by the white paper is a weaker light source, so the colour of its specular reflection is an additive mix of diffuse reflection of light from main light source (light side) + diffuse reflection of light from white paper + specular reflection of light from white paper.
    The diffuse reflection of light from the white paper will be strongest close to the paper and diminish as the surface moves away from it in an upward direction. Thus depending on the relative contributions of these three components, the colour of the specular reflection of light from the white paper will vary across the surface of the sphere and will not be same as the colour of its source (the white paper).

    Attachment 957685
    Image source:www.huevaluechroma.com

    QUESTION 1: Why is the brightness of the paper lower at the back of the sphere compared to the front (80+ vs 65)?
    (front = sunlight through a window, back = ambient light in the room perhaps?)

    QUESTION 2: Specular reflection of light from the cast shadow is the same colour as the cast shadow? (as diffuse reflection of light from the cast shadow should be quite weak?(originating as diffuse reflection of light from ambient light))

    QUESTION 3: You stated that the location of the highlight "is always seen somewhere on the line between the point facing the light source and the visual center of the sphere". With the visual centre do you you mean the actual center of the sphere (see picture)?

    Attachment 957709
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  14. #141
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    briggsy@ashtons Your website was incredibily helpful to me, quite difficult actually but it made me realize the complexity of the subject and it gave me some technical parameters to evaluate and choose colors.
    I'm now trying to merge informations from your site with those from Jason Manley's color theory lesson, who has a less technical and more emotional approach.
    Any opinion about if and how the two sources can complement each other?


    dragonfury where did you take that picture? That place looks familiar to me... Is it Ferrara??
    Last edited by revenebo; April 25th, 2010 at 08:02 AM.
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  15. #142
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    Quote Originally Posted by D.C. View Post
    Although a tough read, the site is the best resource on colour I could find as a beginner. After re-reading things and making notes, things are starting to sink in. I don't know if you still reply to questions, but I would appreciate it if you could point out any errors in my understanding of specular/diffuse reflections:

    1. Every surface can be considered as reflecting diffuse and specular light, where the relative amount of each is dependent on the material of the surface.
    Diffuse reflection of light gives the object its form/colour, specular reflection of light is an image of a light source.

    2. Diffuse reflection of light by the environment (or any object) is a light source for another object (where that object again reflects that light both as diffuse and specular).

    3. Specular reflection results from light that is unchanged by the object and is an ADDITIVE mixture of the colour of the reflected light source and the colour of the reflected diffuse light from the specular's location (following the angle rule).

    Considering the picture below (numbers correspond to brightness levels gathered using color picker).
    The highlight is very bright, thus drowning the diffuse reflection at that location and keeping the colour of the light source.
    However the diffuse reflection of light by the white paper is a weaker light source, so the colour of its specular reflection is an additive mix of diffuse reflection of light from main light source (light side) + diffuse reflection of light from white paper + specular reflection of light from white paper.
    The diffuse reflection of light from the white paper will be strongest close to the paper and diminish as the surface moves away from it in an upward direction. Thus depending on the relative contributions of these three components, the colour of the specular reflection of light from the white paper will vary across the surface of the sphere and will not be same as the colour of its source (the white paper).
    Hi D.C.

    You are a bit of a master of the tough read yourself, but that all sounds like you're on the right track, as long as you keep in mind that the phrase "the colour of the specular reflection" has two possible meanings that you need to stay clear about: it might mean either (A) the overall colour of an area where the specular reflection is the most conspicuous component (as in that last sentence), or (B) the colour of the specular reflection seen as a component of the appearance at that point.


    Quote Originally Posted by D.C. View Post
    QUESTION 1: Why is the brightness of the paper lower at the back of the sphere compared to the front (80+ vs 65)?
    (front = sunlight through a window, back = ambient light in the room perhaps?)

    QUESTION 2: Specular reflection of light from the cast shadow is the same colour as the cast shadow? (as diffuse reflection of light from the cast shadow should be quite weak?(originating as diffuse reflection of light from ambient light))

    QUESTION 3: You stated that the location of the highlight "is always seen somewhere on the line between the point facing the light source and the visual center of the sphere". With the visual centre do you you mean the actual center of the sphere (see picture)?

    1. It's just that the surface to the left of the sphere is further from the main light source.

    2. Yes, if you mean the colour of the specular reflection in sense B above; no, if you mean it in sense A (if it was a red ball, for example, there would be enough light reflected from the tabletop alone to show the local colour in this area)

    3. I was thinking of the centre of the (circular) visual shape of the sphere in the picture plane, though of course this lines up with the physical centre of the sphere.

    Hope that helps!
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  17. #143
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    Hi revenebo

    Very glad you like the site! I'm afraid I didn't see Jason's colour theory lesson, which by all accounts was excellent, but if there any particular issue that is confusing you I'm happy to try to help.
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