Primary Colors part 2: Optical Mixing

[Music] Welcome to Chromosphere, the color theory podcast. My name is Ed Charbono. I am an artist whose main focus is on painting. And I am also an adjunct faculty member in the Fine Arts department at the Minneapolis College of Art and Design. This podcast presents a series of conversations about color, color usage, and optics as they relate to theories of human color perception in the making of visual art and design. For today's episode, I will be continuing the conversation on primary colors. That began in a previous podcast. In that episode, I had gone over subtractive and additive color mixing basics of those two modes of color mixing, as well as talking about complementary colors and some of the history surrounding those systems and those relationships between primary colors and their secondary compliments. Today, I would like to get into talking more specifically about optical mixing. So we have additive, subtractive, and optical mixing. Optical mixing refers to how colors more or less mix on our retinas. There are several different kinds of optical mixing or several different ways that optical mixing takes place. And so with this episode, I'd like to talk specifically about some of those methods and also a little history that takes us back to the times of the impressionists in France. And essentially the mid-late 1800s and a person by the name of Ogden Rude. Ogden Rude, he was a physicist, he was also an artist and a color theorist. He wrote a book published in 1879 called Modern Chromatics, colon with applications to art and industry. It was his intention with this book to write in a very clear way, to write a textbook essentially for people who were non-scientists and specifically for artists. And it's all about color mixing, it's about the properties of light. And he wrote it in a way that summarizes current knowledge at the time about how human color vision operates. And it's written very plainly in very plain language and not a lot of technical mumble-chumble. He writes about Chevrolet, who I've spoken about in other episodes in terms of his role in the defining of simultaneous contrast, as well as after images or what he called successive contrast. He talks about Maxwell, James Clerk Maxwell to be specific, and the spinning discs that he designed to be able to combine different ratios of color that would be spun together and create secondary colors, mix a mixture. And he also talked about Thomas Young and Hermann von Helmholtz, sorry, Helmholtz, and they had just published or within that time era, that general time area, early to mid to late 1800s, had published Helmholtz and Young's theory of trichromacy. I believe that was in around the 1850, 1851 somewhere in there. So he's writing in 1879, and he's summarizing current knowledge of how human color vision works and how that has been demonstrated. And then he's writing about it in terms of how pigments mix as well. So the impressionists painters at the time had gotten their hands on this book, and even though they had been, or and I should go back again and I should say, he describes optical mixing for the first time that I'm aware of. Although he credits some of this thinking, I don't think he was the first, but as far as like this kind of seminal book, he lays it all down and put it all together in an order. And the impressionists got their hands on this book, Rude himself was a painter, and evidently his son, I think his name was Roland. Roland Rude, Roland was also a painter, and he hung around with the impressionist crew. He reported back to his father that guys like Sarat were reading his book and that they actually referred to it as the Bible. Evidently, Rude hated the impressionist so much that he exclaimed then that he wished he had never written his book. They were like, "If that's all I have done for art, I wish I had never written that book. My son, I always knew that a painter could see anything he wanted in nature, but I never before knew that he could see anything he chose in a book." So yeah, I guess the guy really hated Monet. That made me laugh a little whenever I read that. But anyway, what I find to be interesting about this is like for many, many, many years, you know, since I started learning this whole art game, I always heard about the impressionists and that they painted light. They were the painters of light. The light was the subject of the work, and it is the subject. But I don't know if they were like Monet, you know, he painted these haystacks over and over different times of the year and in different lighting conditions. So they were more or less a study of the light and how the light affected the colors did the same with cathedral, the Ruan cathedral, a number of different subjects that he went back to repeatedly. And so hence he's painting the light. Knowing that they were all reading this book, Modern Chromatics by Ogden Rude, and he goes through and writes about all of these things about optics, it makes me think more like, yes, they're painting the light, but that Monet in those studies, he's interested in a concept known as color constancy, which I'll do, that'll be, it's kind of a big topic, it'll be like something for another podcast, but it's essentially how human color vision balances itself to the environment with the available light. So in other words, humans have the capacity to identify a white object under most any light source. We can say that's white, even though if you were to literally say during sunset, there's snow on a haystack, no, that is not white, that's like pink, that's like a shade of red. And I think that this is evidence that Monet was likely exposed to those thoughts as well as other things that were coming about like persistence of vision, which is another one that I'm actually still in the process of learning about myself, and so I don't quite have a handle on it, and I'm actually learning that there isn't a lot of agreement what actually consists of persistence of vision, but I think it has implications on optical mixing as rude was talking about it, as rude described that we will discuss, and basically what it is is it's a positive afterimage, so an afterimage, which we'll probably do a podcast on that too, Chevrolet first identified his second law of successive contrasts or after images as the complement or what's called the supplementary color of an object of a light source. And so you can demonstrate this by wherever you are right now, look at a colorful object for as long as you can without blinking, maybe like a minute or two minutes if you can keep your eyes open that long, and then very quickly divert your gaze to a white or a neutral surface, like a white wall or a white piece of paper or something like that, and you'll see the inverted complementary color or what in the additive, the additive method is referred to as supplemental color floating on that piece of paper or that white plane as this ghost like, and it's the exact opposite of the color that you were just looking at. In the additive system, what are referred to are supplemental colors, they're across from each other on the color wheel. They add up this hence additive to create white. And so in modern chromatics of 1879, [BLANK_AUDIO] Rude goes into great detail to talk about how colors mix on the retina as spectral light and how they mix as paint mixtures or anchor or things that absorb light and reflect other portions of the spectrum. This is a great interest to me because I'm trying to wrap my head around this notion of a color wheel that is where it sees the nature between the subtractive method and the additive method as reciprocal and as linked. And that my knowledge of the additive system helps me to make adjustments in the subtractive system. And so going back to Monet, to me that adds another layer of interest looking at his work. He's really trying to suss out like optically like what is actually happening here rather than just making pretty pictures of like a pond or something. That to me is a lot more interesting to dive into as far as like intellectually and looking at like a painting or something. So optical mixing refers to little particles of color or they can be multiple sizes. Small to big let's say particles of different colors that are placed side by side and around each other. And when we see them especially at a distance they mix optically on our retina so cyan and yellow will mix to make a green color. So if you think of CMYK printing the cyan and the yellow there is no green ink in my printer. And so if I'm printing something and I'm seeing green I'm seeing lots of little dots that are cyan and yellow that are right next to each other and they're very small. So I can't see them individually. So my mind perceives the color green. But that is not to say that we're engaged in the additive system per se. It's still, yeah this is where it gets complicated. So all optical color mixing is subtractive because we're working with pigments. So those two colors of cyan and yellow form green in my mind because they're reflecting in cyan's case blue and green wavelengths and in yellow's case yellow is the product of the reflectance of green and red wavelengths. So cyan is reflecting green. The yellow is reflecting green. Therefore there's more green being reflected back into my eye and perceived by my mind. Then there are the blue and the red wavelengths that are also coming. So we perceive it as green but there is some blue and red wavelengths in there that are actually effectively like dulling the green. So the green isn't as vibrant as it could be with the total absence of any blue or red light. And so that kind of speaks to the limitations of subtractive color mixing and hence how subtractive colors are limited in terms of brightness and chromaticity that can be achieved like on a computer screen or a television. There's a much greater bucket of colors that we can perceive that can't be replicated in in subtractive color mixing which points to some of the troubles between working digitally and then printing that digital image out onto a piece of paper. You're moving from the additive system to the subtractive system. That's a whole can of worms too but we'll get into on another episode because there's a fascinating history about how that has been and is being tackled and tried to figure out. So yeah, different types of optical color mixing include glazing so mixing a pigment into a clear or translucent medium and applying that over other colors or color A color or multiple colors. So you can have multiple glazes and so the light will penetrate through the glazes and get to the surface color and then reflect reflect back out through the glazes again. And so those glazes each layer will be effectively absorbing or subtracting certain wavelengths and reflecting others. And so glazing is a way of doing that and we'll go into more on glazing and future podcasts because there's some interesting stuff there too in terms of film of oil has actually two surfaces the top and the bottom. So the way light goes through it and bounces off the top layer and the bottom layer and how that interacts can create what are called interference colors and all sorts of fun stuff. Yeah, and their stories about how Titian and the Venetian painters would glaze using their hands they use their palms of their hands and their fingers to wipe glazes of color onto their paintings because they could apply it more thinly and more evenly than they could with a brush. Sculubbling is a form of optical mixing or what is known I should actually actually add that a lot of this is referred to as delusive blending. So it's blending of colors by putting little dots or particles next to each other and they delusively blend as opposed to mixing them on a palette where it's all one big goop of one color. Sculubbling is like when you have an effect where let's say the texture of the canvas has got hills and valleys and it's paint at all one color and then you take another color that's kind of dry on the brush and you go across and you just hit the tops of the hills, the peaks and it just kind of puts the paint on like in a freckled way. And so you're not covering up the under layer or you can dust it on take a brush to dry brush and kind of dab it on so the brush marks are leaving like these little freckly marks and you can build up a texture doing that most famously pointalism is a type of optical mixing also known by a bigger umbrella term called divisionism or chroma luminarianism. Whatever that word is that's kind of a umbrella term is divisionism so divisionism this way of painting and especially if you look at like Van Gogh's work this pointalism involves like little dots, Sirot made these paintings with a bunch of little dots, little pin points right. Divisionism is a term that covers a much more wide scope of different types of mark making so you can have like these patches of paint over other fields of color. And if you look at like Van Gogh's paintings and stuff that he was really big on that like with all these little larger brush marks that all went together yet as if you looked at his paintings from a distance they tend to mix optically and then when you get up close to him you can see the texture. Almost as if each brush mark is like a little sculpture of sorts. One of the cool things about Sirot I think is that he tended to follow a pattern of sorts or recipe almost with the arrangement of his dots and so with that painting in the Chicago Art Institute Sunday afternoon in the park or La Grande Jotte I think I'm saying whatever. The painting that was in Ferris-Beeleur's Day Off that painting shows a park scene and the way the colors are arranged not entirely but fairly consistently is that he's got different dots in different orders and so he'll have like a dot for the local color of the objects so like if the person is wearing like a red shirt he's got dots of red. And then next to those dot little dots are red he'll and their spurs small dots of the color of the light source so like an orange is yellow. And then other dots that are from the reflected light of nearby objects so the local color of the grass that the person is sitting on maybe or other objects that are nearby other people. Those he's got dots reflected into the into the composition and then he's got another set of dots that are the compliment of the lights are so blues and violets. So for me learning that and observing it in the work is you know makes it that much more of an in-depth experience because it's that just like he was sitting there just putting a bunch of dots everywhere and just kind of going for it. He had a plan and much of it from what I understand was through knowledge derived from Root's book Modern Chromatics. And so back to the contents of that and what Root is kind of summarizing in the book is to say several things. We've discussed on the podcast before the tri-chromatic theory of color vision where Thomas Young and Herman von Helmholtz theorized and I think it later proven that There are light-sensitive cone cells that respond to different wavelengths of white light to produce all the colors that we can see, and they are chiefly sensitive to red, greens, and blues. Those are the three types of cone cells. There is some redundancy and overlap in those sensitivities. Like the cones that are sensitive to the long wavelengths of red. Those are what they are most sensitive to, but they can also detect wavelengths of green and blue as well. It's just marginal, fractional, and same with the green and the blue. So if your green cones are active, you're able to perceive some of the blue range and the red range with those cones. Rud also writes about the work of James Maxwell, who was a physicist. Yeah, I've heard him described as a link between Newton and Einstein in terms of our understanding of the nature of light as it works both as a wavelength and a particle, which the particle is the photon that the waves of electromagnetic energy are carrying. And Maxwell designed these disks. So they're called Maxwell's disks. And basically, you had a crank motor, maybe, just something simple that you could crank and turn. He made these colored disks, painted different colors. And let's say if you imagine a circle disk, and if you mark the center and you cut a slit in the disk from the center hole out, so you have a radius. And you do this with a red, with a green, with whatever colors. And then you put the disks together. You can slide them together so that more or less of the red and the green are showing. So you could have it be 50% or 40, 60, or whatever. And then you put this disk on the little motor wheel and you crank it. And it starts spinning and those two colors merge optically to create a second color. It would be like probably like a neutral brown or a black in the case of red and green mixing. This is similar to, if you've ever noticed, like a car tire spinning as you're going down the freeway and the spokes of the wheel merge into what looks to be like a solid disk. And I think that this has to do with a phenomenon, like I said earlier, called persistence of vision, but I have to look into that more. Persistence of vision, like I said, is the opposite of an aphor effect. So if you stare at something, the classic example is to look at like a dark object on a bright background. And if you close your eyes and even hold your hand over your eyes, you'll be able to see that image in your mind as this floating image where it'll continue being the dark object on the bright background. And some of the times other colors will enter into that and stuff like that. But basically it's theorized that this phenomenon is like how film works like movies and that there's so many frames per second and that our minds don't perceive the spaces between the pictures, the frames, because we are vision from frame to frame persists and are perception, I should say, the perception of the image persists while it disappears before the new image takes its place. So we can watch a movie without getting like seasick because if you think about it, I'd have to figure out what those spaces are, but there's probably within an hour of movie, there's probably a couple of minutes where you're not seeing anything. But anyway, I think that this could be at the core of how colors mix optically as well, that this blending takes place as we merge these colors in our mind because the memory of the one interjects, stamps itself onto the memory of the other color and hence they mix optically to create a second color. So thinking about optical color mixing, how I was talking about the subtractive and additive models of paint mixing. So the way they're reciprocal is that if I'm mixing a color on my paint palette, what I'm seeing are various mixtures of red, green, blue wavelengths, reflecting off of that substance and appearing in my mind. And the combinations of those pigments, of those colors, I should say, are the adding of light wavelengths to create a color. Now the idea of delusive blending or point-al-ism, CMYK printing is that there's like these little dots that are put next to each other, so the cyan and the yellow make green. Well, the same could be said for pigments and dyes and inks and anything or any type of colorful material that's used in like art and design making images. And that is to say that the mineral that is crushed up for ultramarine blue are just become like very small particles that are then mixed with linseed oil or acrylic or whatever the medium is. But those particles, we just can't see them, they're so small, we can't see that they're all separate. In the case of dyes, the particles might be even smaller than ground mineral pigments. Chromophore is the name for the molecules of things that give off color, chromophore. And in the case of ultramarine blue, a color like ultramarine blue, like synthetic ultramarine blue I should add, sometimes known as French ultramarine. That color in the blue family is much closer to violet than it is to green. And I've seen ultramarine blue is actually that almost just look like violet. One thing about Ruud's book when he's talking about Thomas Young's Helmholtz's theory of trichromacy, he consistently throughout the book lists red, green and violet as the primary colors of light as opposed to red, green and blue RGB. However, checking like Thomas Young's color triangle that he made, he does list the primaries there as red, green and blue. So I still have a little bit of research, a little Sherlock Holmes stuff going on to try to determine, I don't know, where that shift occurred. They commonly refer to the lower wavelengths of light affecting the short wavelengths, I should say, and the short wavelengths cones as being blue and violet sensitive, those are the shortest wavelengths. And I've read or I've encountered information like that our eyes, even though violet is among the shorter wavelengths, our cones are not actually as sensitive to violet. In fact, the sky would not be blue if our eyes were more sensitive to that lower range and that the sky would be violet basically instead of blue because evidently there's many more wavelengths of violet scattered in the sky than there are blue ones. That'll be an episode centering on Homer how he refers to the color of the ocean as the wine dark sea, several times in both the Iliad and the Odyssey. So back to thinking about our color wheel and the reciprocal nature of the additive and subtractive color mixing method, we have red, green and blue or violet. So we're talking about a blue that is very much towards a violet. And then the secondaries are CMY, cyan magenta and yellow which are the primaries of the subtractive mixing method. And so using this as a guide while I'm mixing paint and thinking about the particles that could be microscopic or depending on how finally the pigments are ground. But regardless that the individual pigments just like in pointalism and CMYK printing, they're little dots, they're little specks of things that are reflecting certain wavelengths of light. And so if I'm, if I have my ultrary in blue and I'm thinking that yellow is the complement. So maybe a yellow that is like azo yellow or a hansa yellow on the cooler side of yellow. Mixing those two together. will place the pigment particles side by side and amongst each other within the goo of the paint or the ink or whatever the medium is. And those particles will reflect light that we will perceive via the additive color mixing method in our mind. So the blue, in this case, are synthetic ultramarine blue, which I believe was discovered in the mid-1800s as deposits are leftover stuff on the inside of kilns that they used to bake lime. That could be right or wrong. But yeah, so the traditional lapis lazuli derived ultramarine blue, which is like the historic stuff from this lapis lazuli stone that's mined mainly in Afghanistan, that is a more powdery blue, a lighter blue when it's ground. Actually, it kind of depends on how it's ground and the type of blue that you get out of it. Whereas this synthetic one, I believe, was discovered in these lime kilns or noticed in the early 1800s, mid-1800s, that means more towards the violet side of the family of the blue hues. So what we're looking at, a violet-y blue, but basically that blue is going to be absorbing red and green wavelengths. And it's going to be reflecting blue wavelengths, right? And/or violet, if we think about Ogden Root and his RGB primary colors of the light. And on the other side of the color wheel from that is yellow. So blue and yellow, yeah, and this method are technically complementary. And so mixing that yellow, placing those yellow pigments particles next to the blue, the yellow will be absorbing blue light, reflecting red and green wavelengths. And so since the blue and yellow together are respectively absorbing red and green for the blue and then blue for the yellow, it's basically you're getting towards black because that mixture is absorbing most of the spectrum. And it's reflecting parts of the spectrum as well. The blue is reflecting blue. And the yellow is reflecting red and green. So there again, we have the blue, red, and green trifecta of complementary colors which mix together to create white. But if there's not a lot of light, white reads as gray. So like if you look at a cloud in the sky, and it's a puffy white cloud, that cloud, the water droplets and various elements inside the cloud are scattering and reflecting light and recombining all the wavelengths back into white light. But if the cloud is dense and not a lot of light is actually coming through it, it's still being scattered at an equal rate. It's just that it's darker. There's less light to be perceived. So we see it as a gray cloud or a dark black thunder cloud. So back to our attempt at mixing black with ultramarine blue and Hansi yellow. I believe there's going to be a certain amount of green wavelengths that are going to be a little bit more dominant in the reflection. So that mixture is going to read as a dark green. So then mixing in something like a conachronome magenta or an alizarin crimson, which is in the red family. But that magenta is complementary to the green. And so the magenta will cancel out that green in our mixture. There's a pathway towards mixing like a black color. I guess what we refer to those is chromatic blacks. Because you can make it perfectly neutral. But you can then choose to mix in a little bit more with ultramarine. So you got a black that tips towards blue or violet. And so the black can have some nuance to it if you want that effect. So basically, this color model represents is a way of thinking about this idea that all color is optical mixing. It's just that traditionally with serrata or whatever with the dots or van Gogh with the brush marks. Those are just bigger marks. But the idea that these small particles and they can be microscopic are still behaving in the same way. And therefore, this notion of an attempt towards trying to arrive at a color by mixing the fewest colors together as a challenge or something. I can predict what might be happening by thinking about the wavelengths that each color is reflecting. Because even though we have these primary colors per se, the colors that you buy in tubes of paint don't exactly correspond to the true primary. So in order to mix black or neutral color, they got to be massaged a little bit. Although some of them are pretty close to exact compliments. Like Alizarin Crimson and Thelal Green, that mixes-- so we've got like a magenta and a cream. And that will make, in my experience, like a true black color. This has been the second part of an ongoing conversation about primary colors, their history, and how the additive of the mis subtractive color will-- color mixing methods work in a reciprocal manner. In terms of optical mixing, I think the thing that I keep coming back to is that when considering that we have pigments or dyes, very small particles versus larger dots or pieces of, like if you imagine, a colored pencil being scratched across a piece of paper. It's leaving trace amounts and letting the paper read through as well, and thus optically mixing with the paper. It has to do with the scale of the particles, how the spaces between the particles allow other colors to mix visually on our retinas. So in the case of the white substrate and putting oil paint, taking that pigment and putting it into a linseed oil medium, and thus having a larger mass with the same amount of pigments, I guess it would be. It's just that they're spread out more. So hence it creates or refer to as a translucent glaze. Part of my thinking on this generated by recent readings of a book called Color for the Sciences by Jan Koendrick. In Koendrick's book, in one part, he mentions this idea of scale, and it's how we think about it. Like a tree, at human scale is these pieces like leaves. And then we can see the space between them. But if we were to increase that scale, we wouldn't see if we were to increase our scale in relationship to that tree. Those spaces between the leaves wouldn't be as apparent. So that's what's happening. More microscopic, level, or even, you know, poinelism or something, or CMYK printing, where it's maybe not so much microscopic. It's still smaller than what we're able to perceive the spaces between them. With our human color vision. So it's all about trying to think about the scale of the particles that are reflecting color, and how they're sitting next to each other, or on top of different surfaces, and how, like in the case of glazing or this delusive blending, how those surfaces reflect a white piece of paper, or white photo paper, whatever white thing it has to do with equating the brightness of the reflectivity with the value of that potential reflection. I'm still trying to wrap my head around this kind of stuff. I'll be talking more about Corrender Inks book. He goes into great detail, especially in terms of a person by the name of Wilhelm Otswald. And so this idea of the primary colors part, two is this episode. Part one was more about additive and subtractive color mixing. The future parts will come to include casting a larger net over where some of these concepts are coming from and how they may be working and going into more depth on that. Like in Coinder Inks book, he's got a chapter. Otswald's RGB color model, which is really interesting, and how it explains a lot of visual phenomenon in printing and while in both the additive and subtractive methods. And I'll also keep looking into this idea of persistence of vision and how that may be affecting how these colors merge in our minds. I'm not sure about that. The other thing that I read about it is it could explain how like blinking, how most of the time we're not aware of blinking, but it's an instant where our eyes are closed and it's dark and how that is not noticeable. So the image persists while the blink is going on. And then also back to our mixture of trying to attain a black color by mixing ultramarine blue and as a yellow which at the end I talked about maybe having to add some agenda to that mixture because that mixture may ultimately reflect or be perceived as a greenish tone and not a true black. And part of that could be like I said I'm still learning about this stuff so but part of it could include taken into account a phenomenon called the Prikinji shift which I will have an episode as how it relates perhaps why Mary's robe is blue or one of the reasons maybe that it's blue in Christian art, ultramarine blue. But this Prikinji shift describes or theorizes how our red cones become less perceptive in low light. And so blues and greens and violets will remain more vivid in perception. And so if you think of our mixture of yellow and blue going down in value it's reflecting less light and yellow our perception of yellow is the result of red and green wavelengths stimulating the cones in our eyes and our redness. As that value decreases the brightness the color itself gets more towards black the red cones become less active therefore that yellow which is the product of red and green are green cones they remain strong and start to perceive the green in that yellow as the red diminishes. So it could be that that color actually does go straight towards a true neutral black it's just that human color vision lacks the capability to perceive it so hence having to add a little bit of red in there to help out those red cones wake them up a little bit or massage it with magenta. Yeah so there's a couple of sneak peeks at what may come in the future in this podcast trying to wrap our heads around this idea of visual art and design and perception. And last thought one thing that will become apparent in this series of podcasts to his questions and history related to the relationship between sound and light our perception of electromagnetic energy as a wave and our perception of sound as a wave. And then the attempts of the centuries to not equate the two but to use the terminology of sound and music to describe color and composition in visual arts and design. And so maybe I'll leave you here with thinking about optical mixing this notion of the space between the particles playing as much a role in our perception of the color as as significant a role the space between the pigments as are the pigments themselves. So I thought box maybe Google box Tokata and fugue in D minor that's a piece that in my mind relies heavily on the spaces between the notes to really bring it home. And then also I was thinking Franz lists Hungarian Rhapsody number two the space between the notes what that brings to the piece. So yes, Bach Tokata and fugue in D minor if you google that there's a crazy one on YouTube where they've got these sound bars like this visual like old school 1980s graphics going with it so try and find that one it's really cool. And then yeah, lists Hungarian Rhapsody number two if you're going to listen to that it's almost mandatory that you have to listen to the Melblanc 1950s. Daffy Ducks Rhapsody I'm talking like Daffy Ducks anyway Melblanc Daffy Ducks Rhapsody check that out yes thank you for listening. I hope you enjoyed this episode please share it with your friends and family who may be interested and follow Chromosphere the color theory podcast on Facebook and Instagram. We'd love to hear from you if you have comments or suggestions. I'd like to thank Jeremy Schipinski for writing and performing the theme music. Thank you also to Grant Winkle's Susie Manila and Jeremy Schipinski again for their production consulting and editing.