Additive and Subtractive Color

Additive and Subtractive Color

1. Introduction
   
   
   
   1. What we've been taught - As children, we were taught that the primary colors were red, blue, and yellow.
   
   
   2. What we've been missing - Like many other things back then, we were only given half of the story. This rule was true when mixing paint, but it no longer applies when dealing with projected light, color printing, or computer monitors.
   
   
   3. Thesis – Through an in-depth look at the physical properties of light and perception, it is possible to gain a more thorough understanding of color and its temperamental qualities. The colors we perceive in world around us can be explained through the additive and subtractive color systems.
      
      
      
      1. The Kindergarten Color Wheel……
         
      
      
      2. The Additive Color Wheel…………
         
      
      
      3. The Subtractive color wheel…………
         
      
      
      
      
   
   


2. Background Information
   
   
   
   1. History of color theory - Before we begin to understand how color is perceived, it is important to understand what color is.
   
   
   2. Important people in the evolution of color theory:
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      

      550 BC	Pythagoras
      350 BC	Aristotle
      1611	Aron Sigfrid Forsius
      1646	Athanasius Kircher
      1704	Sir Isaac Newton
      1772	Ignaz Schiferrmüller
      1775	Tibias Mayer
      1810	Phillip Otto Runge
      1839	Michel Eugene Chevreul
      1915	Albert Henry Munsell
      1983	Michel Albert-Vanel

      
      
      
      
      1. Plato Timaeus (360BC)…“The law of proportion according to which the several colours are formed, even if a man knew he would be foolish in telling, for he could not give any necessary reason, nor indeed any tolerable or probably explanation of them.” – Plato Timaeus…light rays do not enter the eye, but rather our eyes emit a ray which bounces off objects
      
      
      2. Aristotle (350BC)…philosopher/scientist; understood that color was a mixture light and darkness and organized seven colors tonally as he himself noted in his paper De sensu et sensibili (On Sense and Sensible Objects); organized light in a linear fashion; his system could be seen in the changing light of a day…the white light of noon becomes tinged with yellow, and changes gradually to orange, and then to red.   After sunset, the evening red becomes purple violet changing to a night sky which appears as dark blue. Then black.
      
      
      3. Robert Grosseteste (early 13 th century) saw light as a “prima material” and developed a system of colours as part of his “grandiose metaphysical interpretation of light” in his book De colore; organized light through a right angle
      
      
      
      4. Robert Hooke…mathematician; believed color was a mixture of light and darkeness; had a scale that went from brilliant red, which was pure while light with the least amount of darkness added, to dull blue, the last step before black, which was the complete extinction of light by darkness
      
      
      5. Leonardo da Vinci – (1510) this artist and engineer developed the technique of “chiaroscuro” (light-dark) and described six “simple colours” – white, yellow, green, blue, black and red; straight lined arrangement of chromatic colours yellow, green, blue and red...interested in colours as a painter…this system maintains today
      
      
      6. Sir Isaac Newton (1642-1726) – modern understanding of light and color started with him; scientist/engineer; first to understand the rainbow
         
         
         
         1. First to understand that color was a byproduct of light and figured out how to separate it using a prism;   the prism could refract light, dividing it into its constituent colors by the first prism, and the resulting bundle of colored rays is reconstituted into white light by the second:
            
            
         
         
         2. The Hue Circle - the first modern explanation of color mixing…additive color mixing; he provided a conceptual arrangement of colors around the circumference of a circle which allowed the painters' primaries (RYB) to be arranged opposite their complementary colors, as a way of denoting that each complementary would enhance the other's effect through optical contrast
            
            
         
         
         3. Perception - color is a perceptual property, not a physical property, which means that the weighting of wavelengths in a light mixture occurs in the eye, not in the light
         
         
         4. Viewed color as a physical problem, involving light striking objects and entering our eyes
         
         
         5. Concluded 7 asymmetric colours with unequal angles
         
         
         
         
      
      
      7. Johann Wolfgang von Goethe (1810)
         
         
         
         1. Published a 1,400 page treatise on color …“That I am the only person in this century who has the right insight into the difficult science of colors, that is what I am rather proud of, and that is what gives me the feeling that I have outstripped many.”
         
         
         2. Thought that Newton was wrong…“As to what I have done as a poet…I take no pride in it…but that in my century I am the only person who knows the truth in the difficult science of colours – of that, I say, I am not a little proud, and here I have a consciousness of a superiority to many.” - Johann Eckermann , Conversations of Goethe , (tr. John Oxenford ), London, 1930, p.302
         
         
         3. Concluded 6 symmetric colours…there are only two pure colours…blue and yellow, the rest are degrees of these; created a double intersecting triangle color wheel
         
         
         4. Realized that the sensations of color reaching our brain are also shaped by our perception – by the mechanics of human vision and by the way our brains process information; what we see of an object depends upon the object, the lighting and our perception
            
            
         
         
         
         
      
      
      8. James Clerk Maxwell – (1831-1879) mathematician and theoretical physicist; the father of additive color; studied the perception of color and color blindness
         
         
      
      
      
      
   
   
   3. What is Light?
      
      
      
      1. Composition – wavelengths
      
      
      2. The Visible Light Spectrum – the portion of the electromagnetic spectrum that is visible by the human eye
      
      
      
      
   
   
   4. What is Color?
      
      
      
      1. The human eye is sensitive to electromagnetic radiation with wavelengths between about 380 and 700 nanometers. This radiation is known as light. The eye has three classes of color-sensitive light receptors called cones, which respond roughly to red, blue and green light (around 650, 530, and 460 nm, respectively). A range of colors can be reproduced by one of two complimentary approached: additive color and subtractive color.
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         
         

         violet	380–450 nm
         blue	450–495 nm
         green	495–570 nm
         yellow	570–590 nm
         orange	590–620 nm
         red	620–750 nm

         
         
      
      
      2. Definition - the byproduct of the spectrum of light, as it is reflected or absorbed, as received by the human eye and processed by the human brain.
      
      
      3. Composition - it is made up of seven wavelength groups…the colors you see are ROYGBIV
      
      
      4. Perception - the cones in our eyes process different wavelengths of color
      
      
      
      
   
   
   
   


3. Additive Color
   
   
   
   1. A. Definition of the additive color system
      
      
      
      
      1. Combined light sources, starting with darkness (black).   The additive primary colors are red(R), green (G), and blue (B).   Adding R and G light makes yellow (Y).   Similarly, G + B = cyan (C) and R + B = magenta (M).   Combining all three additive primaries makes white
      
      
      2. Mixing colors of light is the RGB color model…all paossible colors that can be created by mixing these three colored lights are referred to as the gamus of thos particular lights
      
      
      3. The color we see directly from a light source - the color we see coming emitted directly from a light source before an object reflects the light is created using an additive color model
      
      
      4. Physics - How the eye interprets light wavelengths in the perception of color
      
      
      5. Visible light -   a select part of the electromagnetic spectrum
      
      
      6. Composition of light – Newton's glass prism
      
      
      
      
   
   
   2. Source: beams of light or dots of light on monitor screens
   
   
   3. The additive color wheel
      
      
      
      1. Black plus wavelengths
      
      
      2. Primary colors – red, green, and blue
      
      
      3. Secondary colors – cyan, magenta, and yellow
      
      
      
      
   
   
   4. Application in art – monitors, television, and video projectors all of which use combinations of red, green, and blue phosphors
      
      
      
      1. Computer and TV - each pixel starts out black and color is added
      
      
      2. Stage lights - used to illuminate actors on stage…greenscreen gels
      
      
      3. Image capture devices - digital cameras, flatbed scanner, video cameras
      
      
      4. Used for monitor screens and most image file formats…there are actually a number of RGB color spaces – sRBG, Adobe RGB 1998, Bruce RGB, Chrome 2000, etc. – differing from each other in the purity of their primary colors, which affects their gamut
         
         
         
         1. The Adobe RGB color space (1998) and location of primaries and white point; designed to encompass most of the colors achievable on CMYK color printers by using RBG primary colors on a device such as the computer display
            
            
         
         
         2. sRGB color space created cooperatively by HP and Microsoft for use on monitors, printers and the Internet (1995)
            
            
         
         
         
         
      
      
      
      
   
   
   
   


4. Subtractive Color
   
   
   
   1. Definition of the subtractive color system
      
      
      
      
      1. Illuminate objects that contain dyes or pigments that remove portions of the visible spectrum.   The objects may eithertransmit light (transparencies) or reflect light (paper).   The subtractive primaries are C, M, and Y.   Cyan absorbs red; hence C is sometimes called “minus red” (-R).   Similarly, M is –G and Y is –B.
      
      
      2. As colors are subtracted to produce white
      
      
      3. The color we see bounced off of an object – a red apple is not red, it simply absorbs all wavelengths other than red
      
      
      4. The frequencies not absorbed – we see white light minus any colors absorbed by the material the light bounces off of
      
      
      5. Interpretive – depends many factors such as the material of the object
      
      
      
      
   
   
   2. Source: objects that transmit or reflect light: film or prints; typically illuminated by white light
   
   
   3. The subtractive color wheel
      
      
      
      1. White minus wavelengths
      
      
      2. Primary colors – cyan, magenta, and yellow
      
      
      3. Secondary colors – red, green, blue
      
      
      
      
   
   
   4. Application in art
      
      
      
      1. In printing, the mix gives a muddy black, so normally true black ink is used as well…CMYK where the K stands for key”
      
      
      2. Painting and Drawing - paint absorbs most of the light frequencies and reflects back only the wavelength that defines the color you see; painters mix their paints to shape the light reflected from a painting, and the viewer's eye interprets this reflected light as color
      
      
      3. Print Photography, magazine ads, posters - the offset printing process uses cmyk…ink is transparent and absorbs light as the colors are layered on the paper…to be reproducible on a press, an original color image, such as a photograph, must first be converted into a patter of small dots for each of the four colors.
         
         
      
      
      4. Fabric dyes
      
      
      5. RYB color model; it is possible to mix red, yellow, and blue paint to get orange, purple and a n on-primary shade of green paint due to subtractive mixing; this model is largely used for traditional reasons; red and blue are in fact approximations for magenta and cyan respectively; the CMY color model can more easily display a full gamut of colors than can RYB
      
      
      
      
   
   
   
   


5. Color Gamut
   
   
   
   1. Definition of the color gamut
      
      
      
      1. The set of possible colors within a color system – defined by
      
      
      2. Limitations - Additive and subtractive color systems reproduce their own subset of all visible color
         
         
         
         
         
         
      
      
      
      
   
   
   2. How does this affect us?
      
      
      
      
      1. Additive to subtractive model – computer monitor to printed works
      
      
      2. Subtractive to additive model – scanned or photographed works
      
      
      
      
   
   
   3. What can we do?
      
      
      
      1. Print – use colors only within the color gamut of the system your final piece will be in…digital art must be converted to CMYK color for print…some printers prefer RGB with ICC profiles attached as this allows the printer to use color management methods when converting to CMYK
      
      
      2. Digital – adjust H,V,S of images once they are scanned or captured
      
      
      3. Larger color spaces contain both more colors and brighter, more saturated colors; if your camera or scanner supports it, use a larger color space such as Adobe RGB; use sRGB for web graphics. This is at least in the same ballpark as most monitors.   Using adobe RBG for web images leads to washed-out looking colors in applications that are not color aware (i.e. most web browsers)
      
      
      
      
   
   
   
   


6. Conclusion
   
   
   
   1. Two extremes of color experience - We have learned that painters mix their paints to shape the light reflected from a painting, and the viewer's eye interprets this reflected light as color. These two extremes of color experience – the mixed paints, and the interpreting eye – are described by two separate and unequal color-mixing theories.
   
   
   2. As artist we should be aware – in order to have more control about the exact look of your colors, you much be aware of the limitations of color in each form