The Dimensions of Colour - a colour theory discussion thread

[VirgL]

Hey Doc,
I've previously asked you questions, and you always been a source of enlightement
Though I understand the presence of diffuse and specular reflection on an object, im still trying to understand how light is physically reacting in some cases. Lights is either bounced or absorbed as I understand, however i still dont understand why I see some of the things i see.

The main exemple i could give you, is a black, polished, bowling ball, with bright white specular on it.
So the black comes from most of the light being absorbed by the ball and thus not a lot of light bounce back to the eye.. but you got that specular reflection that does contain white, or any color the environement could have. I think I understand why different surface have different speculars ( Prometheus tutorials explains it very weel, and makes a lot of sense )

But the question here is why can we see a bright specular reflection on a dark object, if photons are supposed to be absorbed almost competely, and not bounced back on dark objects?

If specular reflections is created by the object having a coating making everything shiny, shouldnt it completely override the underlying diffuse reflection ?

I Hope these questions make some sense
Thanks for taking time to read this.

[briggsy@ashtons]

Excellent question Virg.

The thing that Prometheus' tutorial doesn't explain is that specular and diffuse reflection are two distinct processes that occur simultaneously on most objects. The specular (or "interface") reflection, which generally remains the colour of the light source, is thought to consist of light that bounces at the surface. The diffuse (or "body") reflection is light that penetrates the surface and re-emerges more or less equally in all directions, often coloured by the object. For example if you look at an orange you will see the light-source coloured specular reflection as well as the orange-coloured diffuse reflection. An uneven surface makes the specular reflection fuzzy, but this fuzzy specular is an entirely different thing to the diffuse or body reflection.

So in your polished black ball, the part of the light that penetrates the surface is largely absorbed, but the part of the light that doesn't penetrate the surface is not affected, and produces the usual interface reflection that you see whatever the colour of the ball.

[VirgL]

That makes a lot of sense, thank you very much for the answer !

[VirgL]

Hello again Mr.briggsy
I'm still seeking some answers or thoughts on a specific aspect of colors, and again, im asking for your precious help. I hope im not getting annoying ,im thinking others could read this and wanting to ask similars questions, so why not ask

This question concern mostly , color harmony , not color harmony in sense of emotion or psychological effect that specific colors are supposed to create to the viewer, but color harmony, as a ''rule'' that defines the amount of temperature shift that occur between light and shadow in a specific light situation.

Your probably seeing my question coming but here it is.
How do you make sure, all the colors in your picture obey to the same color harmony?

Im painting mostly digitally, and use the HSB color picker in photoshop, and your 3d space color system made a lot of sense to me, be cause it is something logical to me, where i can define extremes, a point A and a point B ( A=light B=shadow ) and can imply concious decision of colors and not just random color guessing.

So, as I understand, and tried to applied so far, different hues, either desaturate or get more saturated depending of the location of the color of the light source on the color wheel.

So how do you make sure all your colors have the same diagonal 3d color space , in a specific light situation. And properly place A and B for all colors?

I have know idea how traditional painter manage to do this, my guess is they use the same amount of pigment in each color equally to change their temperature equally.

Thanks so much for sharing all your expertise ! And sorry for my amateur english.

[Elwell]

I have know idea how traditional painter manage to do this, my guess is they use the same amount of pigment in each color equally to change their temperature equally.

Actually, because of the complexities of pigment, that won't work. Most traditional painters do it the same way most digital painters do it: by eye.

[briggsy@ashtons]

Virg

Paint the (coloured) light and shade pattern that would be caused by each light source alone as a separate layer, then overlay these layers in LINEAR DODGE mode over a black background. Vary the strength of each light source by varying the opacity of its layer, and try to keep the total brightness down so that nothing "clips" against maximum brightness (B=100). You can apply the local colours of objects using a MULTIPLY layer on the top. If that all makes sense I'd love to see what you come up with!

There's no equivalent procedure for traditional paints, so if anyone is not satisfied with eyeballing with those I'd suggest working from a digital colour study that you make first, using this method.

[VirgL]

hello, thanks for your replies Elwell And Briggsy.

Briggsy: I started to explore various light situation using the technique you mentionned in your last post. Its really quite interesting. Im trying to get an easier understanding and see if theres reoccuring patterns as the result of the mixing of the local hue of the object in relationship with the hue of the lightsource. At which point of the wheel will a color start decreasing more in S than in H.
I just had a couple of questions, maybe you can help me.
I noticed a difference between the blending modes in photoshop CS vs Photoshop CS4
in CS4 the Linear Dodge is also named ( additive ) and seems to do proper additive mixing.
But the Linear Dodge in Photoshop CS seems to gives different result depending of which layer is on top. I tried the Screen blending mode and it seems to do proper additice blending ??

I'll show you what I come up with, ill probably post some stuff in my sketchbook and share you the link so you can give me some feedback I dont want to spam your thread with pictures.

Thanks !

[briggsy@ashtons]

Thanks Virg. One tip for your experiments: avoid fully saturated colours (S = 100) for your objects and lightsources, as these don't exist in nature, and can give you some strange results.

I don't know why CS would behave differently to CS4. You're not in a different Image Mode in CS are you? Linear Dodge is exactly additive while Screen Mode is quasi-additive in a way that is less prone to clipping against the limits of the RGB gamut.

I'll keep an eye on your sketchbook but please feel free to post anything you want here.

[briggsy@ashtons]

If you've looked at The Dimensions of Colour, it won't surprise you that I'm very pleased that James Gurney's new book "doesn't contain recipes for mixing colours or step by step painting procedures" (Color and Light, p. 9). Much much better, it shows how an artist of his calibre thinks about colour and light.

Any single book on this subject can only be an introduction, but what an introduction this is! The book is very generously illustrated with his own works, plus those of many of his favourite past masters. These images fully justify their place by showing us what it is possible to achieve, especially from the imagination, by those who are willing to go beyond a simplistic approach to "colour theory".

Gurney admits that when he set out to write the book, he himself at first underestimated the complexity of the subject (p. 222), and that he had to research aspects of physics and visual perception more deeply than he had previously. I suspect it's no coincidence that some of his most perfectly realized imaginative paintings, including the sleeping dinosaur on the cover and Titanoboa on p. 165, are from 2009.

The modern books and websites recommended by Gurney for further reading (pp. 220-1) will probably be the most accessible resources for the next steps in your explorations, but it may be worth mentioning that many of the older texts he lists are available for free download or reading online:

Chevreul, Michel Eugène, 1839. The principles of harmony and contrast of colours ... (1860 Eng. tr. by Charles Martel).
http://books.google.com/books?id=LIMOAAAAQAAJ

Goethe, Johann Wolfgang, 1810. Goethe's Theory of Colours (partial English tr. of Zur Farbenlehre by Eastlake, 1840).
http://www.archive.org/details/goeth...ryco00goetgoog
http://edoc.hu-berlin.de/ebind/hdok/...xml?part=thumb (German edn plates)

Guptill, Arthur L., 1935. Color in sketching and rendering.
http://hdl.handle.net/2027/mdp.39015009248579 (read online)

Hatt, J.Arthur H., 1908. The colorist.
http://books.google.com.au/books?id=3f_VAAAAMAAJ (US access only)

Hawthorne, Charles Webster, 1938. Hawthorne on painting.
http://www.archive.org/details/hawthorneonpaint00hawt (Daisy/borrow)
http://www.archive.org/details/collectionofnote00hawt (NEW LINK WITH PDF)

Minnaert, Arcel G.J., 1954. The nature of light and colour in the open air.
http://hdl.handle.net/2027/mdp.39015065972997 (read online)

Munsell, Albert H. 1905. A color notation. An illustrated system defining all colors and their relations by measured scales of hue, value, and chroma.
http://www.archive.org/details/acolornotation00munsgoog (1st edn)
http://www.archive.org/details/colornotation00muns (5th edn, 1919)

Munsell, Albert H. 1913. Color balance illustrated.
http://www.archive.org/details/color...ated00munsiala

Pollock, Montagu, 1903. Light and water, a study of reflexion and colour in river, lake, and sea.
http://www.archive.org/details/light...udyo00polluoft

Rood, Ogden, 1879. Modern chromatics, with applications to art and industry.
http://www.archive.org/details/cu31924031167889

Ross, Deman Waldo, 1912. On painting and drawing.
http://www.archive.org/details/ondra...dpai04rossgoog

Ruskin, John, 1843. Modern painters, Volume 1.
http://www.archive.org/details/modernpainters01rusk (1888 edn)

Ruskin, John, 1857. The elements of drawing. With 8 illustrations drawn by the author.
http://www.archive.org/details/elementsofdraw00ruskuoft (1920? edn)

I'm quite certain that Color and Light will mark the beginning of the end for the simplistic approach to color that still predominates in art teaching. If you are an art or design student, get this book, study it, and then pester your teachers ceaselessly until THEY study it.

At the moment you can buy Color and Light from Better World Books for only US$15.98, with free shipping in the US and only US$3.97 worldwide.
http://www.betterworldbooks.com/colo...740797719.aspx

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Edit: James Gurney's comment on Dimensions of Colour!

"David Briggs is none other than the mastermind behind the website "Dimensions of Color". It’s one of the best resources on light and color on the Internet. I owe much of what I’ve learned on the topic to Mr. Briggs. ..."

- James Gurney
http://gurneyjourney.blogspot.com/20...-teachers.html

[jams]

I won't be posting any art here for awhile, because I have nothing worth showing yet, but I just joined the forum to give briggsy a huge "thank you!"
I've never seen color explained so well or so in-depth. Seriously, it seems like nobody knows what the hell they're talking about when it comes to color, so finding this here is awesome. Looking forward to finally learning how color actually works over the next few days. This is gonna change the way I paint forever!

Thanks again, briggsy! =)

[guidosalimbeni]

Hi,
i'm new to the forum as a registered member but it has been a while that i'm following the forum and this thread specially. Thankyou very much for all the info and the superb website Brigg!!

I thought i was in the right track of learning the color theory you so well explained and i came into this page on the book called "painting light - the hidden techniques of the impressionists" that i attch..

My question is that : under 2 sources of illumination which one is red and the other is pale yellow (as in the last ill of the image) the cast shadow "of" the red source light thend toward green... I thought this was created by the princeple of simultaneous contrast and that can be seen only by the human eye and not by a camera.. now i'm a bit confused.. i tried to figure out why the shadow looks greenish in this shadow but i could not find a solution.. can you give some advise? thanks

[draw]

I think the Gurney works look like paintings of photographs whereas something like a claude lorraine although not as 'coloured' looks like a painting of 'life'.

IMO All the colour theory in the world will not produce a 'life'like atmospheric relationship if its not painted without a sound gestalt tonal conception and for me ends up with that well entrenched copying photographic look. For me that is the difference between illustration and art.

If there are some examples to the contrary I would love to see the contrast.

[briggsy@ashtons]

Well guidosalimbeni, you're looking at the image with a human eye (I assume), so why would'nt you expect to see "simultaneous contrast"? The image colours of the shadows on the right are much the same in all three pictures - they're all a very low-chroma orange grey (check for yourself in Photoshop!). The greenish hue we see in the bottom right one could be said to be the result of "simultaneous contrast", although I think that term is used for more than one kind of effect. In cases like this I think it's the automatic color correction filter in our brains coming up with a slightly wrong answer. (The shadow is less red than everything else, so our brains "assign" a slightly greenish colour to it).

Welcome aboard, by the way, to you and jams - Hope to hear from you guys here often!

[briggsy@ashtons]

I'm scratching my head over a few things in that, draw, but I guess the main point is that I would have thought that the ultimate aim of undestanding colour (for some painters anyway) would be to obtain a "sound gestalt tonal conception". I'm wondering what you think of Tim Miller, for example, who we both know has an intense interest in understanding colour and light.

[guidosalimbeni]

i checked in photoshop!! thankyou very much.. guido

[briggsy@ashtons]

I posted this little tutorial yesterday in another thread for someone who was having trouble with making up the effect of coloured lighting, and thought I'd post it here as well, so it won't sink out of sight.

With Linear Dodge you can easily "clip" the upper limit of your RGB gamut and start getting strange results; if that happens you just need to keep your colours a bit darker.

Bear in mind that the procedure applies directly only to this simple situation, and will lead you into trouble if you apply it blindly to more complex situations. Try instead to understand the reasons for each step.

Also bear in mind always that these tips are meant as aids to getting physically correct colour relationships when that is what you are after, not orders to get those relationships. Plenty of lovely painting styles do not use "correct" colour and lighting, or correct perspective or anatomy, for that matter.

[draw]

Thanks for this David... a very effective tutorial

[spinor]

Dear Dr. Briggs,

Thank you so much for your invaluable website! have been reading it the whole days and i feel like i just had a new birth! I've been painting digitally for a while but always confused by how to pick up colors. Now you made everything so clear to me. Thousand thanks!!!

Xi

[bbshrmn]

hi and thank you again for taking the time to answer these questions. as per your suggestion in the email, i will post them here so everyone can benefit. these were the major points of confusion that i forgot to ask.

in faber birren's book 'creative color' he mentions, "the most beautiful of all formal color gradations that is known" as the "uniform chroma scale-which have the same apparent color content but which differ in lightness and darkness." is that in fact, the same thing as your described "uniform saturation shading series?" (if its not, how are they related as to what happens in nature?)

if so, he also suggests an "easy" method of making one of these scales by mixing a tint, a tone, and a shade of the same hue and then intermixing them for in-between steps. if this is the case it raises questions.

1. doesn't much care still need to be taken with the tint, tone and shade to ensure they are constant in color saturation amongst themselves? this doesnt just happen naturally, right?
2. assuming you have step 1(question 1) done correct, is he implying that all in-between steps will then be balanced, saturation wise, inherently? if so, by that logic, couldnt i do away with mixing the tone all together and just use the tint and the shade to make the tone? and if not then it would seem this whole approach falls apart a bit.
3. lastly, if i use red, add black and then a bit more red again to bring it back on the saturation line, couldnt i have just used less black to begin with or is it not the same thing? how does this affect step one?

ok, sorry, i guess there is one other thing as well. so what is the proof/evidence that this is actually true and that saturation doesnt decrease or increase in the shadows? im guessing the shoddy results of just color sampling images isnt enough.

thank you thank you, very much appreciated.

[briggsy@ashtons]

You're welcome, draw and spinor!

Thanks for taking the trouble, Bob. They're all very good questions.

Birren's "uniform chroma scales"

in faber birren's book 'creative color' he mentions, "the most beautiful of all formal color gradations that is known" as the "uniform chroma scale-which have the same apparent color content but which differ in lightness and darkness." is that in fact, the same thing as your described "uniform saturation shading series?" (if its not, how are they related as to what happens in nature?)

What Birren calls "uniform chroma scales" are the perceptual (or logarithmic) "isochromes" of the Ostwald system, which is not really used any more. Ostwald's perceptual isochromes were in theory lines of uniform saturation in my terminology, though in practice (in the Ostwald colour atlas) they seem to me to be somewhere between lines of uniform saturation and lines of uniform chroma.


Mixing a shading series

1. doesn't much care still need to be taken with the tint, tone and shade to ensure they are constant in color saturation amongst themselves? this doesnt just happen naturally, right?
2. assuming you have step 1(question 1) done correct, is he implying that all in-between steps will then be balanced, saturation wise, inherently? if so, by that logic, couldnt i do away with mixing the tone all together and just use the tint and the shade to make the tone? and if not then it would seem this whole approach falls apart a bit.
3. lastly, if i use red, add black and then a bit more red again to bring it back on the saturation line, couldnt i have just used less black to begin with or is it not the same thing? how does this affect step one?

1. Of course, and of course.
2. Mixtures between successive steps tend to drift off the uniform saturation line, so the steps should be kept close together.
3. if you are shading red+black+white by adding black, you correct the saturation with red (not red+black+white). If you are shading a pure opaque red with black, there is less of a tendency for the saturation to drop, but if it does you could boost the saturation with a transparent red. Adding some of the opaque red would of course just take you back in the direction you came from).


Uniform-saturation series and illumination

ok, sorry, i guess there is one other thing as well. so what is the proof/evidence that this is actually true and that saturation doesnt decrease or increase in the shadows? im guessing the shoddy results of just color sampling images isnt enough.

I'll answer that by showing you some uniform saturation series and asking what you see. The main rectangle of the attached jpg simply shows seven uniform saturation series (one achromatic). We automatically see it as an image of uniform object colours under varying illumination. To me this simple demonstration neatly proves that
(1) our visual system recognizes relationships of uniform saturation in the visual field, and
(2) it uses these relationships in its amazing capacity to separate effects of illumination from effects of object colour (object-colour constancy).

[bbshrmn]

I'll answer that by showing you some uniform saturation series and asking what you see. The main rectangle of the attached jpg simply shows seven uniform saturation series (one achromatic). We automatically see it as an image of uniform object colours under varying illumination. To me this simple demonstration neatly proves that
(1) our visual system recognizes relationships of uniform saturation in the visual field, and
(2) it uses these relationships in its amazing capacity to separate effects of illumination from effects of object colour (object-colour constancy).

thanks for the quick reply.

... but does this example, starting out with some colors that arent so crisp and saturated to begin with, not work just as well? this reads very natural and as uniform object colors also, no?

[Elwell]

What Birren calls "uniform chroma scales" are the perceptual (or logarithmic) "isochromes" of the Ostwald system, which is not really used any more.

And thank goodness for that! Creative Color is overall a good book, but Birren's big flaw was his attachment to Ostwald.

[briggsy@ashtons]

... but does this example, starting out with some colors that arent so crisp and saturated to begin with, not work just as well? this reads very natural and as uniform object colors also, no?

Not as natural as when you shade the same colours keeping the saturation uniform:

[bbshrmn]

Not as natural as when you shade the same colours keeping the saturation uniform:

yeah, it appears so. given that its the same illumination range, your colors definitely appear to be passing into the darkness, where mine feel to be coming out of it a bit. thank you thats helpful.

i was also trying to color sample some HDR images to see what kind of results i would get since they are supposed to be closer to how we perceive reality and i did find mostly uniform saturation throughout them. that said, the saturation was often at 100%. if you will accept the loose terms, why the 'blow out' and are these HDR images better for us to study, from a 'reality standpoint'? are they just constantly pushing the outer limits of the technologies involved, how does this relate to paint?

thank you.

[briggsy@ashtons]

Sorry, Bob, I'm a bit vague on the details of HDR image processing at the moment, so I'll have to pass on those four(!) new questions for now. A digital camera is in a way a kind of inexpensive spectrophotometer, and you can very usefully investigate some things using digital photos, but I'd be much more inclined to use a straightforward image, aware of its limitations, than one that is higly manipulated in a way I don't fully understand.

[bbshrmn]

ok, thank you and sorry for the bombardment. so much to know and so little time.

[Jie Kageshinzo]

I decided to go back to the basics and learn as much as I can about value, saturation and hue, and I would just like to say that, as much as how your site gave me a headache trying to understand it on my own, thanks so much for such an invaluable resource Briggsy.

As of the moment, I'm alternating between Gnomon Workshop's Light and Color and your website for studying, and already, my brain is trying to understand the difference between chroma and saturation, and I feel my brain bleeding. I'll continue my reading and studying and hopefully, once I get familiar with the technical aspects of the subject, everything will be that much clearer for me.

Thanks!

[briggsy@ashtons]

Everything about colour is more complicated than many people assume, so a little bit of bleeding is probably a good sign! Saturation especially is a word that requires caution, because it has several different meanings, which people using the word are often not conscious of.

Some people use the word "saturation" for the purity of colours of surfaces, with these colours being considered as mixtures of white, "pure colour", and black, and saturation as the proportion of the "pure colour" component in the mix. People who say that chroma is "very similar" to saturation may simply be confused, but they may also be using saturation in this sense, which in effect means relative chroma - i.e. chroma as a percentage of the chroma of the "pure colour". This concept of "pure colour" is very problematic in relation to surfaces, however, so the open ended scale of chroma is much better.

In Photoshop, saturation is the colour purity of the light that is emitted from the screen. Any light can be considered to be a mixture of a certain percentage of white light, plus coloured light: saturation in this sense is simply one minus the proportion of white light. I use saturation in this second sense, as explained on this page:
http://www.huevaluechroma.com/093.php

Colours like B and C in Figure 9.8 on that page have low chroma, and low saturation in the first sense, because as surface colours they contain a lot of black, but they have high saturation in the second sense, because the light given off is pure red (only the red phosphors are glowing).

Not sure if that will help or not, but anyway a close study of the figure I just mentioned usually seems to get the idea across.

[Valentino]

I'd like to pose a technical question. I am quite familiar with the color theory in general (we had that class back at Academy), and rules and guidelines in particular, yet there are some instances in which I am not 100% certain about the correct procedure.

For instance, one of those guidelines is that the lightest dark is darker than the darkest light. (It is not always valid. I mean - it only applies to certain kinds of light under certain conditions. In overcast light, such rules do not apply. Even in sunlight, a very light ground surface can significantly raise shadow values.)

What I'd like to know is how one shoud draw an area in light which local hue is equally dark or darker than the shadow? Take an apple for instance (or people with really ruddy cheeks). Apple may be yellow/green in hue, appearing rather high value in light, but there is large dark red spot which is partially in light and partially in shadow. That intense, dark red is of equal value as adjacent shadow. If one draws it as he sees it, the drawing may look somewhat odd; the apple will appear flat with oddly looking shadow. I mean - form shadow will go nicely around the form, creating the illusion of roundness, but the shape of adjacent red spot of equal value will confuse the viewer. What one should do in that case?

Should one neglect what he sees in order to create a convincing illusion of form? Should he draw the mentioned dark spot (or say, ruddy cheeks) lighter than it appears, in order to prevent merging it with the shape of the shadow ?

[briggsy@ashtons]

I'm really glad you brought this up Valentino, because this particular piece of advice is doled out far too often on these forums. It's not just that it's wrong factually, it's also very bad teaching to hand out simplistic "rules" instead of encouraging analysis and understanding.

You're perfectly correct that the rule only applies under certain conditions. The brightness of any point is the brightness of the illumination multiplied by the reflectance of the surface. It should be clear from this diagram that the rule can not possibly hold if there are dark and light local colours involved, unless the contrast between the illumination in the light and in the shadow is very high. If the rule has any validity it is as a statement of aesthetic preference, not physical fact.



It would be better to say "Always make your lighting so contrasty that the lightest shadow is darker than the darkest light". At least that would make the limitations of the "rule" more obvious.

I don't agree that painting your subject as it appears, ignoring the rule, will make it "appear flat" or create an "oddly looking shadow". All it will do is cause the pattern of lights and darks in your picture to differ a little from the pattern of light and shadow. That's it!