The Dimensions of Colour - a colour theory discussion thread - Page 5
Join the #1 Art Workshop - LevelUpJoin Premium Art Workshop

Page 5 of 12 FirstFirst 1 2 3 4 5 6 7 8 9 10 11 12 LastLast
Results 121 to 150 of 333

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

  1. #121
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    Whoa! I've just had a massive spike in the visitor stats and it's all from deviantART. Did somebody there make me site of the day or something?

    Reply With Quote Reply With Quote  

  2. #122
    Join Date
    Aug 2009
    Posts
    6
    Thanks
    103
    Thanked 7 Times in 3 Posts
    Follows
    0
    Following
    0

    Thanks for the insights!

    So I read through the dimensions of color web page and my little mind had difficulty handling it. So many terms I didn't know! But I muscled through it as I know I have been especially weak on color and I need to figure it out if I am ever going to get better, even if it took me the better part of a week to get through it. Thanks for the resource! I wish I were in Australia so I could do one of your classes and really get a handle on the subject. If you ever put up videos of your classes or instruction I'd definitely watch them even if they were filmed by a 6 year old with a web cam.

    Since I am so weak on my color theory I have been attempting little (frustrating) exercises by myself. One I have tried is using the color picker to watch what the color sliders do when I sample across different parts of a photograph. I was quite pleased to discover that the saturation (chroma?) really does pretty much stay the same as value changes across a uniform surface like a red ball as long as its not reflecting too much. Though I am still boggled as can be about trying to replicate skin which moves hue saturation and value all over the place. Is it because skin is translucent and has blood vessels below it or is it subsurface scattering of light or how skin is also oily and a bit reflective or is it because skin is not all the same color/texture/thickness, or maybe because I am looking at photos with multiple light sources ...?

    I attempted the ball exercise and this is what I came up with. I definitely still have a long way to go. But if I squint really really hard... and take off my glasses...



    If anyone knows some really good resources or a really solid and simple way to think about and approach color, I'd love to hear it. I'd especially love it if someone had a blood oath guarded life or death super secret about color torn from the hands of an ancient and mysterious conspiracy of history's phenomenal artists. There have to be secrets about this... right?

    Reply With Quote Reply With Quote  

  3. #123
    Join Date
    Aug 2003
    Location
    Montreal, QC
    Posts
    1,007
    Thanks
    333
    Thanked 220 Times in 183 Posts
    Follows
    0
    Following
    0
    Amazing thread, I spend the last week reading all the information on your website, going over it again and again.. I must thank you endlessly for all this free information, im glad the web was invented because a lot of artist would not benefit from all this information since we dont all go to art school
    The uniform saturation principle really opened my eyes , i used to think like a lot of people that the saturation would vary all the way on a lit sphere ( even with a white light ) The fact that most photos i was studying had a colored ambient + a color light source would always deform that fact and i could never figure how much the hue and saturation should change while the planes receed. If I understand everything right, the only changes in hue and saturation on a surface ( lit by white light only in this case ) would be cause by specular reflection ? Like Zaorr pointed, I think Loomis was probably confusing the 2 in his observation, he would saw diffuse specular reflection as a part of the diffuse reflection since it was probably the lightest part of the lit area, and only considering the light source as the only thing that can be reflected in a specular reflection. Im still unsure of where to place the drastical point of change in temperature from light side to shadow side in the case of ; lets say a warm light vs a cold ambient, it seems the be a bit before the terminator on the light side of the sphere but im probably wrong..
    The last part of your webpage where you help artist apply those principle with paint was really helpful, thanks again Mr.Briggsy

    Reply With Quote Reply With Quote  

  4. #124
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    Quote Originally Posted by dragonfury View Post
    I wish I were in Australia so I could do one of your classes and really get a handle on the subject. If you ever put up videos of your classes or instruction I'd definitely watch them even if they were filmed by a 6 year old with a web cam.
    Come on, airfares are cheap right now and my next digital colour course starts at the end of this month. See you there? Anyway, I'm more than happy to comment on anything you post here.

    Quote Originally Posted by dragonfury View Post
    Though I am still boggled as can be about trying to replicate skin which moves hue saturation and value all over the place. Is it because skin is translucent and has blood vessels below it or is it subsurface scattering of light or how skin is also oily and a bit reflective or is it because skin is not all the same color/texture/thickness, or maybe because I am looking at photos with multiple light sources ...?
    All of the above! Skin really looks wrong if it is painted in one colour all over. Look for all those variations and paint them in without overdoing them.

    Quote Originally Posted by dragonfury View Post
    I attempted the ball exercise and this is what I came up with. I definitely still have a long way to go. But if I squint really really hard... and take off my glasses...
    I can't put a precise figure on it (for lack of exactly comparable objects) but I think I would have put in the cast shadow a tad lighter (apart from the crevice shadow). Otherwise it looks great to me.

    Quote Originally Posted by dragonfury View Post
    I'd especially love it if someone had a blood oath guarded life or death super secret about color torn from the hands of an ancient and mysterious conspiracy of history's phenomenal artists. There have to be secrets about this... right?
    Actually I think that many of history's phenomenal artists would have killed to know what we know about colour today. In most cases their secret is ... hard work, continuous immersion and long experience. Having said that, there is a lot of useful information on painting techniques in various historical documents - what period are you most interested in?

    Reply With Quote Reply With Quote  

  5. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


  6. #125
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    Quote Originally Posted by WhiteC View Post
    Amazing thread, I spend the last week reading all the information on your website, going over it again and again.. I must thank you endlessly for all this free information, im glad the web was invented because a lot of artist would not benefit from all this information since we dont all go to art school
    Actually it's because of what you most likely would and wouldn't have been told about colour if you did go to art school that I wrote the thing!

    Whatever people think about it, the web is inevitably creating a "loaves and fishes" situation. If everyone, or even a substantial minority, provides one valuable thing for free, we all end up far richer than we would ever get by trying to flog off our own private tutorial/ebook/album etc.

    Quote Originally Posted by WhiteC View Post
    Im still unsure of where to place the drastical point of change in temperature from light side to shadow side in the case of ; lets say a warm light vs a cold ambient, it seems the be a bit before the terminator on the light side of the sphere but im probably wrong..
    As you approach the terminator the main light drops off rapidly, and so the ambient light increasingly influences the colour. Beyond the terminator, glare from the main light source may influence the colour for some distance (think of the effect of the sun on the blue sky just beside it). So you often see a transition on both sides of the terminator.

    Quote Originally Posted by WhiteC View Post
    thanks again Mr.Briggsy
    Ahem, it's Dr Briggsy, thank you

    Reply With Quote Reply With Quote  

  7. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


  8. #126
    Join Date
    Aug 2003
    Location
    Montreal, QC
    Posts
    1,007
    Thanks
    333
    Thanked 220 Times in 183 Posts
    Follows
    0
    Following
    0
    just checked if anyone had replied before i went to bed, thanks a lot for your answer.

    Just to be sure, by glare you mean some kind of blur ???

    Also , if you allow me , since i forgot to post in my previous post ; your talking somewhere in this thread that you only use screen, multipy and normal modes in photoshop for your demonstration, i understand how you use multiply and screen but about normal mode, do you use it only for specular reflection and atmospheric perspective ?? ( like in the case of that red sphere on a blue background )

    anyway thanks doctor thats definitely clarifying a lot of things, I hope this thread will live on for a long tim

    Cheers,

    Last edited by VirgL; August 31st, 2009 at 11:00 PM. Reason: spelling
    Reply With Quote Reply With Quote  

  9. #127
    Join Date
    Aug 2009
    Posts
    6
    Thanks
    103
    Thanked 7 Times in 3 Posts
    Follows
    0
    Following
    0
    Thanks for the response! The shadow was something I really couldn't figure out that well since most the other ones seemed to drop straight down to the ground with a bit of ambient light softening their edges, though with your observation I am thinking that I was looking at the crevice shadow instead of the drop shadow. I'm glad the colors worked though for the ball though because that is what I really focused on.

    If I could use color like anyone it would be Joaquín Sorolla for how he communicates light's behavior so well, Thomas Moran for landscapes and atmosphere (though that might have been the location of where he was painting more than his own creativity), and probably William Bouguereau for people who more so than a photograph look ALIVE. That is an odd mix, but each of those aspects of their work really floors me. Though my favorite artist at the moment is Alphons Mucha, his colors don't attract me nearly as much as his line work and design, though in some of his pieces the color is phenomenal as well. So if you could tell me their secrets that would be grand. I am noticing that some of them used a lot less color than I thought they did, so that is interesting (well, except sorolla, it looks like his paintings are exploding with light).

    I lightened the shadow up a bit.



    As for airfare to the sister colony, I think the trip would cost more than my university tuition when all was said and done .

    Reply With Quote Reply With Quote  

  10. #128
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    WhiteC

    Glad if I helped. In mentioning glare I was thinking that if there is even the slightest atmospheric haze, then adjacent to a strong light source like the sun you will get some white sunlight added to the blue skylight. (Indoors, light reflected off the ceiling adjacent to a light bulb will similarly cause a gradational rather than a completely sharp fall-off of the influence of the light).

    dragonfury

    The shadow looks good now - congratulations and thanks so much for contributing!

    Regarding painting techniques, do you know about the Rational Painting forum? You'll find threads on the techniques of many of the painters that you like (a heated 30+ page thread debating the technique of Bouguereau, for instance).
    http://rationalpainting.org

    If you like Mucha for composition, have you seen his Lectures on Art?
    http://www.amazon.com/gp/product/085670296X

    Reply With Quote Reply With Quote  

  11. The Following 2 Users Say Thank You to briggsy@ashtons For This Useful Post:


  12. #129
    OmenSpirits's Avatar
    OmenSpirits is offline Commercial-Illustrator in-training, NOT an artist. Level 13 Gladiator: Retiarius
    Join Date
    Jan 2008
    Location
    Birth Place of the World, NYC
    Posts
    2,826
    Thanks
    2,622
    Thanked 1,042 Times in 680 Posts
    Follows
    0
    Following
    0
    "Everything must serve the idea. The means used to convey the idea should be the simplest and clear. Just what is required. No extra images. To me this is a universal principle of art. Saying as much as possible with a minimum of means."
    -John Huston, Director
    Reply With Quote Reply With Quote  

  13. #130
    Join Date
    Apr 2008
    Posts
    1,232
    Thanks
    679
    Thanked 861 Times in 364 Posts
    Follows
    0
    Following
    0
    Hi David.
    Here's the questions i mentioned the other day. : )

    Ok, here in your site you say:
    T_onal painters would observe this difference in brightness and "colorfulness" of light, and represent it with paint areas of different lightness and chroma, in order to create the illusion of a surface of uniform chroma under varying light
    I was wondering, what is a "tonal painter" exactly? I couldn't find a proper definition.
    Also, several times you wrote about how its better to use uniform saturation for realism (than higher saturation in the half light e.g), ok but when do you recommend not using uniform saturation? I find it doesnt always give pleasing results even after adding specular and bounce light. Also more often than not in photos, saturation is more or less higher in the shadows and although i hear colors are not accurate in photos i'd appreciate your thoughts on all this.

    Just for confirmation now: specular light is additive right? So, to reuse the example of a red ball, if there were a bright green wall behind the ball, its receding "planes", affected by the specular light from the wall should get a little... yellowish?

    Another thing; according to you, are there some significant advantages for photoshop users to work in lab mode rather than rgb? Then again i heard various things but would like an informed opinion.

    Finally, i always wondered why, often under sunlight, there's a saturated reddish rim of color at the shadow edge on human skin, somewhat like in this photo (im aware it's completely blown out but couldn't find any better).
    Oh and more for the sake of curiosity than anyhthing i'd like to know the formula used to calculate the lowest row of the chart here (brightness).

    I guess that's all. :)

    Thanks a lot for your time and any infos on these questions.

    Last edited by SM; September 29th, 2009 at 01:56 PM.
    Reply With Quote Reply With Quote  

  14. #131
    Join Date
    Mar 2009
    Location
    Brazil / Berkeley, CA
    Posts
    140
    Thanks
    51
    Thanked 36 Times in 24 Posts
    Follows
    0
    Following
    0
    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!

    Reply With Quote Reply With Quote  

  15. #132
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    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 09:48 PM.
    Reply With Quote Reply With Quote  

  16. The Following User Says Thank You to briggsy@ashtons For This Useful Post:

    SM

  17. #133
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    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.

    Reply With Quote Reply With Quote  

  18. The Following 5 Users Say Thank You to briggsy@ashtons For This Useful Post:


  19. #134
    Join Date
    Nov 2007
    Location
    Toronto
    Posts
    791
    Thanks
    423
    Thanked 295 Times in 144 Posts
    Follows
    0
    Following
    0
    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 11:40 AM.
    Reply With Quote Reply With Quote  

  20. #135
    Join Date
    Sep 2009
    Location
    Canada
    Posts
    120
    Thanks
    35
    Thanked 39 Times in 26 Posts
    Follows
    0
    Following
    0
    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 =)
    Reply With Quote Reply With Quote  

  21. #136
    Join Date
    Sep 2007
    Posts
    522
    Thanks
    76
    Thanked 177 Times in 139 Posts
    Follows
    0
    Following
    0
    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
    [[Sketchbook]]
    Reply With Quote Reply With Quote  

  22. #137
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    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

    --------------------------------------------------------------------------


    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!

    Attached Images Attached Images  
    Reply With Quote Reply With Quote  

  23. #138
    Join Date
    Feb 2010
    Location
    Orange County, CA
    Posts
    21
    Thanks
    6
    Thanked 1 Time in 1 Post
    Follows
    0
    Following
    0
    This is so helpful! Thanks so much!

    Reply With Quote Reply With Quote  

  24. #139
    Join Date
    Nov 2007
    Location
    Milwaukee, Wisconsin
    Posts
    143
    Thanks
    9
    Thanked 13 Times in 10 Posts
    Follows
    0
    Following
    0
    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'.

    sketchbook
    blog

    support your local library!
    Reply With Quote Reply With Quote  

  25. #140
    Join Date
    Jul 2008
    Location
    Here
    Posts
    281
    Thanks
    56
    Thanked 63 Times in 48 Posts
    Follows
    0
    Following
    0
    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).

    Name:  2-1a.jpg
Views: 2387
Size:  61.5 KB
    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)?

    Name:  2-1a3.jpg
Views: 2337
Size:  60.7 KB

    Reply With Quote Reply With Quote  

  26. #141
    revenebo's Avatar
    revenebo is offline orchitect and designerd
    Level 6 Gladiator: Provocator
    Join Date
    Jan 2007
    Location
    Italy
    Posts
    742
    Thanks
    359
    Thanked 233 Times in 160 Posts
    Follows
    0
    Following
    0
    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.
    Reply With Quote Reply With Quote  

  27. #142
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    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!

    Reply With Quote Reply With Quote  

  28. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


  29. #143
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    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.

    Reply With Quote Reply With Quote  

  30. #144
    Join Date
    Jul 2008
    Location
    Here
    Posts
    281
    Thanks
    56
    Thanked 63 Times in 48 Posts
    Follows
    0
    Following
    0
    Thanks briggsy@ashtons for your reply. You're right that the wording of my post was quite confusing, I had trouble understanding it after re-reading it again :p, sorry about that.

    1. It's just that the surface to the left of the sphere is further from the main light source.
    Is this because the rays of the main light source are not parallel to each other (light source is not a point light source)? As I understand it, the brightness of a surface facing a light source with parallel rays (like the sun) should be uniform across that surface and vary depending at what angle that surface is facing the light source.
    Of course if the surface is big and its farthest point facing the light source is much farther than its closest point to the light source a noticeable difference would occur?

    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)
    Sorry, yeah I meant B. I was actually thinking about how the brightness varied in that region and what influenced it.

    Generally, how does the total light reflected of other objects behave as a light source? For example, in your picture, will the diffuse reflection from white paper (tabletop) illuminate the sphere uniformly, will it decrease as the surface turns away from the paper (like with a regular light source), is it strongest closest to the paper? Also does specular light reflected from an object contribute to illumination of other objects (with specular light I mean the part of light reflected at any point on a surface that follows the angle rule).

    These questions arose when I tried painting a simple red cube in photoshop. I couldn't figure out how the ground (white canvas, e.g. white paper) would influence the lighting of the cube and how a potential specular reflection of the ground (white canvas) would look like: uniform in brightness across the surface of the cube or decreasing in brightness from bottom towards the top of the cube.

    Last edited by D.C.; April 27th, 2010 at 08:44 PM. Reason: grammar
    Reply With Quote Reply With Quote  

  31. #145
    Elwell's Avatar
    Elwell is offline Sticks Like Grim Death Level 17 Gladiator: Spartacus' Dimachaeri
    Join Date
    May 2003
    Location
    Hudson River valley, NY
    Posts
    16,212
    Thanks
    4,879
    Thanked 16,666 Times in 5,020 Posts
    Follows
    0
    Following
    0
    Quote Originally Posted by D.C. View Post
    Of course if the surface is big and its farthest point facing the light source is much farther than its closest point to the light source a noticeable difference would occur?
    That's it. The intensity of light falls off predictably, according to the inverse square law. With a small light source close to an object, this gradation is very evident.


    Tristan Elwell
    **Finished Work Thread **Process Thread **Edges Tutorial

    Crash Course for Artists, Illustrators, and Cartoonists, NYC, the 2013 Edition!

    "Work is more fun than fun."
    -John Cale

    "Art is supposed to punch you in the brain, and it's supposed to stay punched."
    -Marc Maron
    Reply With Quote Reply With Quote  

  32. The Following User Says Thank You to Elwell For This Useful Post:


  33. #146
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    Yes, the main effect is the roughly inverse square fall-off of light flux with distance; but the decreasing angle of incidence of the light rays to the surface, which I think D.C. was suggesting as the explanation, is a distinct though secondary factor.

    D.C., to answer the second part of your question you need to understand that the inverse square law applies precisely only to a point source of light; with larger light sources the fall-off is slower, and at the theoretical extreme of a wall of light extending infinitely in all directions, it turns out that there isn't any fall-off of light with distance. (You can demonstrate this by bringing up a white page on your monitor in a darkened room, and observing the minimal fall-off of light on objects up to a few cm from the screen). So you would expect little fall-off of light with distance from the table top on the vertical faces of your cube, whereas you do see it on objects like the sphere that curve away from facing the table top.

    Reply With Quote Reply With Quote  

  34. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


  35. #147
    revenebo's Avatar
    revenebo is offline orchitect and designerd
    Level 6 Gladiator: Provocator
    Join Date
    Jan 2007
    Location
    Italy
    Posts
    742
    Thanks
    359
    Thanked 233 Times in 160 Posts
    Follows
    0
    Following
    0
    briggsy@ashtons no issue in particular, it's more about a general sense of disorientation between a "mathematical" approach and an emotional approach based on eyeballing, taste and experience given by exercise.
    I've seen many great artworks, both traditional and digital, that are quite off if compared to the mechanics of light and color you explained and yet they look awesome. In particular it looks like saturation of colors is subject to personal taste and choices.
    I usually try to stick to your instruction when painting (digitally) but, assuming I apply them correctly, I feel that sometimes the result is a little bit boring, in particular in works from imagination. Can the technical parameters be stretched or overlooked in order to convey mood and emotions without screwing up a painting? To what extent?

    PS I know it's a vague question but as I said I'm a bit puzzled by all the info about color theory I'm assimilating...

    Last edited by revenebo; May 2nd, 2010 at 06:16 AM.
    Reply With Quote Reply With Quote  

  36. #148
    Join Date
    May 2005
    Location
    Sydney
    Posts
    810
    Thanks
    187
    Thanked 1,366 Times in 319 Posts
    Follows
    0
    Following
    0
    I think its's a valid question. To me, theory is not there to tell you what to do, but to help you to do what you want to do. Take anatomy for example - just because you understand anatomy, it doesn't mean you can only draw "boring" accurately-proportioned humans. Artists who understand anatomy can draw better monsters, aliens or even spaceships than those who don't, because they can use their knowledge in the service of their imagination and emotion.

    That's how it should be with light and colour. Certainly if you are trying to get a vivid sense of lighting and atmosphere, whether from life or from the imagination, then there are some relationships that you need to get right. But you are free to play with these relationships creatively as well as to report them objectively. To give two examples that are only just a beginning, you can obtain very beautiful effects by accurately transposing those relationships to a very limited tonal and/or colour range, or by transposing the shadow colours to suggest the effect of simultaneous contrast. Obviously this is a step beyond the basic theory, not a step short of it.

    By the way, I'm not at all opposed to eyeballing. As I say somewhere on the site, I think eyeballing rather than mathematical precision is generally sufficient for painting if you understand the relationships involved. All of the spheres in my diagrams for the site were painted by eyeballing the fall-off of light rather than mathematically calculating it.

    Reply With Quote Reply With Quote  

  37. The Following 4 Users Say Thank You to briggsy@ashtons For This Useful Post:


  38. #149
    Join Date
    Jun 2008
    Posts
    184
    Thanks
    11
    Thanked 3 Times in 3 Posts
    Follows
    0
    Following
    0
    Hi,

    I just wanna say I have read the colour theory stuff on your website.It is a little confusing to assimilate all those stuff but I am slowly getting it and it has improved my knowledge on colour.But I am a little confused cause I am normally into 3d stuff.All I do is model stuff,add the texture and set up my light,hit the render button and voila!!!I get my artwork.
    Let me see if I am getting this right:
    Lets say I have a sphere and I decided to give it say a red colour,towards the light,you will probably have 4 tones:shaded part(desaturated)dark red----half light(lighter dark red slightly desaturated)---full light(saturated red)----highlight(white).

    Right?I understand some people do grayscale but that ain't working for me.I would have drawn a sphere but I am too busy to do so.Wonderful thread,keep it up,briggsy@ashtons.

    Reply With Quote Reply With Quote  

  39. #150
    Join Date
    Aug 2010
    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Follows
    0
    Following
    0
    First post on this wonderful site! I just read thru the above color theory principles and added more insight to my rudimentary understanding. Thanks for all the input!

    Reply With Quote Reply With Quote  

Page 5 of 12 FirstFirst 1 2 3 4 5 6 7 8 9 10 11 12 LastLast

Members who have read this thread: 244

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •