Color theory

An essential question for the artist

A blue-covered book is still a blue-covered book, whether it's in the light or in the dark. But this color exists through our light-receiving organ, the eye, only when the object is illuminated by natural or artificial light.

Early work on light

Isaac Newton (1642-1727) and Thomas Young (1773-1829) established some fundamental principles from their work on light, which revealed that color was linked to light radiation. Newton demonstrated that white light could be broken down into a set of visible colors, those of the spectrum. Taking the reverse experiment of recomposing light a step further, Young defined that only three colors were sufficient to reproduce it: indigo blue, yellow, red and green. red and green.

Isaac Newton, famous for his contributions to physics, carried out revolutionary experiments on light in the 17th century. One of his most important discoveries was the decomposition of white light into a colored spectrum. By passing a ray of light through a prism, Newton observed that light decomposed into a palette of colors ranging from red to orange, yellow to green, blue to indigo, and finally ending in violet. This decomposition of white light into different wavelengths revolutionized our understanding of the nature of light.

Thomas Young revolutionized the understanding of light by establishing the theory of the three primary colors. Based on his experiments, he demonstrated that the combination of indigo blue, red and green made it possible to reproduce all visible colors. This discovery paved the way for numerous practical applications, notably in photography, television and color printing.

Light absorption and reflection

Light radiation emitted by a light source can considerably influence the perceived color of objects that absorb or reflect it. For example, a red object will appear that color because it absorbs the wavelengths corresponding to red and reflects the others. Similarly, sunlight, composed of different luminous radiations, can alter the color of objects depending on their chemical composition and their ability to absorb or diffuse light.

1. White bodies reflect all colors ; 2 Black bodies absorb all colors ; 3 Gray bodies absorb and reflect equal amounts of red, green and indigo blue ; 4. Yellow bodies absorb indigo blue and reflect red and green; 5. A magenta body reflects indigo blue and red, and absorbs green; 6. A cyan surface absorbs red and reflects indigo blue and green.

But what do we mean by "color"?

On the one hand, color is the sensation generated by the effect on our retina of receiving light of different wavelengths (between 400 and 760 nanometers). On the other hand, through the principle of absorption and reflection, light is a property of objects subjected to luminous radiation.

Additive and subtractive synthesis

Color-light

Additive synthesis follows directly from the principle of absorption and reflection of light. By observing a beam of white light, we can deduce that light colors can be separated into fundamental light colors and secondary light colors.

Additive synthesis

As illustrated in figure A below, the color white (1) results from the combination of three elementary light colors: green, red and indigo blue. When superimposed in pairs, these fundamental light colors give rise to secondary light colors, such as yellow.

By combining green and red, we obtain magenta by combining red and indigo blue.

Graphic illustration of the concept of additive color synthesis: the white luminosity in the center emanates from the combination of the three fundamental hues of light: bright green, orange-red and indigo blue. Mixing these three colors in pairs produces the composite or secondary hues: yellow, magenta and cyan.

Complementary light colors

The combination of red and green produces a yellow hue, which is complementary to blue, a luminous color absent from this mixture. Magenta complements green, while cyan opposes red.

Subtractive synthesis: color-pigments

Physicists manipulate light colors, while painters use pigment colors, coloring substances capable of covering a surface. They are made up of a pigment and a binder, generally refined linseed oil in the case of oil painting. These shades can be transparent, semi-opaque or opaque. Colors are mixed by subtractive synthesis.

Subtractive synthesis

Subtractive synthesis painting is based on the principle of mixing pigments to absorb certain wavelengths of light. When you superimpose layers of transparent colors, each pigment absorbs a portion of the incident light, allowing the remaining wavelengths to pass through. For example, mixing cyan, magenta and yellow creates black, as these pigments absorb red, green and blue respectively, the three components of white light.

Complementary colors-pigments

The combination of the primary pigment colors cyan and magenta produces a secondary color, indigo blue. This hue is complementary to the primary color yellow, which was not used in the mixture. Consequently, indigo blue is complementary to yellow and vice versa. Similarly, orange-red is complementary to cyan and vice versa. Finally, bright green is complementary to magenta and vice versa.

Conclusion

Understanding the basic principle

Subtractive synthesis in painting is based on a fundamental principle: the combination of colored pigments to create new hues. Unlike the additive synthesis used in lighting, where colors are added together to form the whiteSubtractive synthesis involves the subtraction of certain wavelengths of white light to produce colors. This process relies on the selective absorption of incident light wavelengths by the pigments present in the paint. It is this absorption that creates the colors we perceive.

Interaction of color pigments

Pigments used in paint can be divided into three main categories: primary pigments, secondary pigments and tertiary pigments. Primary pigments are the basic colors that cannot be obtained by mixing, such as cyan, magenta and yellow. By mixing these pigments, we obtain secondary pigments, such as green, orange and violet. Finally, tertiary pigments are created by combining primary and secondary pigments. The subtle interaction of these colored pigments produces a wide range of hues and shades in paint.

Reflection and absorption phenomena

Each colored pigment has a unique spectral signature that determines which wavelengths of light it absorbs and which it reflects. For example, a red pigment absorbs mainly green and blue wavelengths, giving our eyes the perception of red color. This phenomenon of reflection and absorption is essential to understanding how colors form and interact in subtractive synthesis in painting. By judiciously combining different pigments, artists can create rich, vibrant visual compositions.

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