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August 28th, 2010 #151
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.
Hide this ad by registering as a memberAugust 29th, 2010 #152
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.
August 29th, 2010 #153
September 17th, 2010 #154
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.
September 17th, 2010 #155
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September 18th, 2010 #156
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.
September 28th, 2010 #157
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.
October 1st, 2010 #158
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.
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December 21st, 2010 #159
Colour and Light, by James Gurney
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).
Goethe, Johann Wolfgang, 1810. Goethe's Theory of Colours (partial English tr. of Zur Farbenlehre by Eastlake, 1840).
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/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.
Pollock, Montagu, 1903. Light and water, a study of reflexion and colour in river, lake, and sea.
Rood, Ogden, 1879. Modern chromatics, with applications to art and industry.
Ross, Deman Waldo, 1912. On painting and drawing.
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.
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
Last edited by briggsy@ashtons; January 26th, 2012 at 09:19 PM. Reason: New link
December 23rd, 2010 #160Registered User
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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! =)
January 10th, 2011 #161Registered User
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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
January 10th, 2011 #162
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.
January 10th, 2011 #163
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!
Last edited by briggsy@ashtons; January 10th, 2011 at 08:03 AM.
January 10th, 2011 #164
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.
January 10th, 2011 #165Registered User
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i checked in photoshop!! thankyou very much.. guido
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