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The colour wheels of art, perception, science and physiology
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Optics & Laser Technology 38 (2006) 219–229 www.elsevier.com/locate/optlastec
The colour wheels of art, perception, science and physiology Nick Harkness,1 Nick Harkness Pty Ltd., Birdcage 3.1, 65 Doody Street, South Sydney Corporate Park, Alexandria NSW 2015, Australia Available online 15 August 2005
Abstract Colour is not the domain of any one discipline be it art, philosophy, psychology or science. Each discipline has its own colour wheel and this presentation examines the origins and philosophies behind the colour circles of Art, Perception, Science and Physiology (after image) with reference to Aristotle, Robert Boyle, Leonardo da Vinci, Goethe, Ewald Hering and Albert Munsell. The paper analyses and discusses the differences between the four colour wheels using the Natural Colour Systems notation as the reference for hue (the position of colours within each of the colour wheels). Examination of the colour wheels shows the dominance of blue in the wheels of art, science and physiology particularly at the expense of green. This paper does not consider the three-dimensionality of colour space its goal was to review the hue of a colour with regard to its position on the respective colour wheels. r 2005 Elsevier Ltd. All rights reserved. Keywords: CIE L a b ; Colour circles; Colour wheels; Elementary colours; Primary colours; The Natural Colour Systems; The Munsell system
1. Introduction In June 2003 I attended a 5-day residential Colour Summer School run by the Scandinavian Colour Institute at Gripsho¨lm, near Stockholm, Sweden. Out of the 22 attendees only one (myself) was scientifically trained the rest being from non-scientific design or art backgrounds. The course leaders were the international colour educators Berit Bergstro¨m, Chief Executive Officer, Scandinavian Colour School, and Professor Grete Smedal, University of Bergen, Norway. With my background in instrumental colour measurement, this became a trans-disciplinary experience for me, including mixing artist colours, exercises on colour memory, colour combinations and simultaneous contrast.
Corresponding author. Tel.: +61 2 9700 8110; 61 2 9700 8112.
E-mail address: [email protected]. Also at: Chair, Colour Society of Australia Organising Committee for International Colour Association Congress 2009, Sydney. 1
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The paper reports the results of my project, an examination of the colour wheels of art, perception, science and physiology. The preoccupation with colour wheels or circles is intriguing, the rainbow is a bow but within the bow the colours, running from red to violet, are each a continuum and show linearity across the bow (Fig. 1). The rainbow can also form a circle when viewed from an aircraft and Scheuchzer 1731 observed their circularity, i.e. when looking down on a waterfall [1]. Within these circles the colours are again a continuum and exhibit linearity along the radii. Similarly, a scientific (physics) interpretation of the visible spectrum of daylight also gives linearity from blue to red. The visible wavelength range, nominally spans between 400 and 700 nm. Below 400 nm is ultraviolet radiation which we (subjectively) cannot see but can feel through sunburn and above 700 nm there is infra-red radiation which again is invisible but warming. The spectrum is non-circular (Fig. 2). To seek a solution to this possible enigma requires a study of the mechanism of colour vision and the spectral
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Fig. 3. CIE 1931 2 colour matching functions x¯ l y¯ l z¯ l . Fig. 1. Rainbow (do you have a better image on file?).
Fig. 2. Spectral Power Distribution CIE Illuminant D65.
sensitivity of the cones which provide us with colour vision. Examination of the CIE (the International Commission on Illumination) 1931 21 colour matching functions x¯ l , y¯ l & z¯ l reveals distinct peaks for the spectral sensitivity of both the medium wavelength cone y¯ l (green) at 555 nm and the short wave length cone z¯ l (blue) at 445 nm. The long wave length cone x¯ l (red), however, has two peaks, at 600 nm (primary) and 440 nm (secondary) lying below the peak for the short wave length cone (Fig. 3). The CIE 1931 x, y Chromaticity diagram (Fig. 4) was derived from these colour matching functions and the two ends of the spectral locus are joined together, completing the ‘‘circle’’ with the non-spectral colours which are mixtures of long and short wavelength light which we perceive as mixtures of blue and red. A combination of the primary peak sensitivity of the short
wavelength cone (blue) and the secondary peak of the long wavelength cone (red). In this examination of the colour wheels the NCSs colour notation system has been used as the reference for hue, (where hue is a colour’s position on a colour wheel) [2]. NCSs notation describes a colour’s hue in terms of a visual combination of the four chromatic colours we imagine to be pure colours i.e. blue, green, red, and yellow. NCSs notation defines four quadrants based on combinations of two of these four ‘‘pure’’ colours, giving yellow-red, red-blue, blue-green and greenyellow. Examples are Y40R a yellow with a 40% visual attribute towards redness and G60Y a green with a 60% visual attribute towards yellowness. NCSs notation provides a very suitable reference for comparing the configuration of hues on the different wheels, originating from the work based on a perceptual point of view initiated by Ewald Hering [3] .This is based on the concept that we perceive six pure or elementary colours, namely the achromatic white, and black and the chromatic blue, green, red, and yellow. Any colour can be described in terms of its visual relationship to a combination of a number of these six ‘‘pure’’ colours but as explained later there cannot be a relationship which includes yellow and blue together nor red and green. NCSs notation characterizes colours and differences between colours perceptually. Among Hering’s goals was: ‘‘in any event we would have a quantitative comparison of colour differences only, and not a measure of colour itself’’ [3].
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Fig. 4. CIE 1931 Chromaticity Diagram.
2. The colour wheel of art In the context of art, the Irish physicist Robert Boyle proposed: ‘‘There are but few Simple and Primary colours (if I may so call them) from whose various compositions all the rest do as it were result. For though painters can imitate the Hues (though not always the splendour) of those numberless differing colours that are to be met with in the works of nature, and of art, I have not yet found, that to exhibit this strange Variety they need imploy any more than white and black, and red, and blue and yellow and these variously compounded, and (if I may so speak) decompounded, being sufficient to exhibit a variety and number of colours’’ [4]. We first consider then the context of art and design. This uses the classic Johanne Itten [5], colour wheel based on the three primaries of art red, yellow and blue (Fig. 5), as taught in primary school. To produce my first colour wheel I selected gouache paints yellow (process), red (vermilion) and blue (cobalt blue). (It should be noted that the artist does have a palette from which a multitude of blues, reds and yellows and combinations can be selected to develop an artistic colour wheel). My selection resulted not in the expected colour wheel of Johannes Itten, but a beautiful chromatic and dynamic orange, then a purple—a mud colour would be a better description—and a green closer to khaki. (Fig. 6) This necessitated a revisit of the primary colours. There are two sets of primaries depending on whether
Fig. 5. Johannes Itten Colour Wheel.
the colour mixing is additive or subtractive. In the first case we have, red, green and blue, which are the primaries of light, used for example in television and computer monitors. H.G. Grassman (1853), whose laws form the basis of modern colorimetry, stated that each of the three additive primary colours cannot be made by a mixture of the other two primaries (or a mixture of other colours). For example purple is a reddish blue or a bluish red and orange is a yellowish red or a reddish
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Fig. 8. Subtractive Primaries.
Fig. 6. Colour Wheel of ‘‘Art’’ 1.
and mixing these together tends towards blackness, more light being absorbed (or subtracted) as more pigments are added. (Fig. 8) The secondaries of additive colour mixing (yellow, magenta and cyan) can be considered to be the true primaries of subtractive colour mixing, rather than red, yellow and blue. As stated above the artist has an extensive palette from which to select a red (bluish or yellowish), yellow (greenish or reddish) and blue (greenish or reddish). An artist may describe yellow, magenta and cyan as the ‘‘process’’ primaries (together with black) rather than being the ‘‘traditional’’ primaries of art. Likewise red, blue and green can be considered to be the true secondaries of subtractive mixing and not orange, purple and green. For my second attempt process yellow, magenta (a bluish red) and cyan (to me similar in colour to the pure visual blue of NCSs were selected, and as shown in (Fig. 9) even with my limited artistic skills to ‘‘my perception’’ a ‘‘perfect’’ colour wheel was produced.
Fig. 7. Additive Primaries.
3. The colour wheel of perception yellow. Red, however, cannot be a purplish orange or an orange purple. Combining red, green and blue light results in white light. The secondaries of additive colour mixing are yellow (green light plus red light), cyan (blue plus green) and magenta (blue plus red) (Fig. 7). The primaries of light are also the primaries of vision as noted above. We typically refer to the short, medium and long wave length cones as the blue, green and red cones. This description was first used by Thomas Young and Herman Ludwig Ferdinand von Helmholtz. Subtractive colour mixing, on the other hand refers to mixtures of pigments and dyestuffs which absorb light
It has already been noted that with visual colour perception rather than three primaries six pure or elementary colours are used, white, black, red, green, yellow and blue. It might be thought to be wrong to include green as it is considered to be a mixture between blue and yellow. However, while a yellowish red or yellowish green are possible, perception does not allow a bluish yellow nor a yellowish blue. In fact, a pure green is possible which has neither a ‘bluishness’ nor ‘yellowishness’. Wittgenstein [6]. As far back as circa 1480 Leonardo da Vinci, in his ‘‘Treatise on Painting’’ circa 1480, argued that there were six elementary colours;
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Fig. 10. Aron Sigfrid Forsius 1603, Physica Manuskripts 1611.
Fig. 9. Colour Wheel of ‘‘Art’’ 2.
‘‘The first of all simple colours is white, though philosophers will not acknowledge either white or black to be colours; because the first is the cause, or the receiver of colours and the other totally deprived of them. But as painters cannot do without either, we shall place them among the others; and according to this order of things, white will be the first, yellow the second, green the third, blue the fourth, red the fifth, and black the six. We shall set down white for the representative of light, without which no colour can be seen; yellow for earth; green for water, blue for air, red for fire; and black for total darkness’’ Kemp [7]
contribute to our current understanding of the mechanism of colour vision, namely Young and Helmholtz at the first stage of the colour vision process—the cone level—and Hering at the second or perceptual stage. Hering also defined a colour triangle [3]: If we imagine a clear red of a specific hue placed at one corner (r) of a triangle, a completely pure white at the second corner (w), and a completely pure black at the third corner (b) then all possible transitions from clear red to pure white can be arranged along the line (r) to (w), and all transitions between clear red and pure black along the line connecting (r) and (b). As the distance from clear red increases, the colors thus ordered would be continuously more veiled by white on one side and by black on the other until finally all trace of redness vanished in pure white or black .
In his Physica Manuskript (1611) [8], Aron Sigfrid Forsius, Professor of Astronomy in Uppsala, Sweden also referred to these six elementary colours: ‘‘among the colours there are two basic colours white and black . . .. the four intermediate colours are red, blue, green and yellow—and grey from white to black—and these increase in intensity by degrees. . . changing from white by paling or to black by darkening’’. Professor Forsius arranged these six elementary colours and their mixtures in what appears to be a twodimensional diagram. (Fig. 10). In 1878, the psychologist Ewald Hering proposed his opponent colour theory of colour vision based on four psychological primaries: red, green, yellow and blue, where red—green and yellow— blue have a postulated opponent psychological relationship. Hering’s hypothesis appears initially to be in conflict with those of Thomas Young and Helmholtz which are based on the three primaries of colour vision: red, green and blue. Both the latter are in fact partially correct and
(w)
(r)
(b)
Hering’s triangles, which rotate over all hues with the achromatic axis at the centre, make an important contribution to the concept of the three-dimensionality of colour space.
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Philipp Otto Runge’s (1810) design of a colour solid was similarly related to three-dimensional colour space. This was a sphere based on the tints (reductions of the pure colour with white), tones (reductions with grey) and shades (reductions with black). In 1979, the Swedish researchers Anders Ha˚rd, Gunnar Tonnquist and Lars Sivik introduced the Natural Colour Systems. The rationale was stated by Tonnquist (Scandinavian Colour Institute): ‘‘As a system in first hand shall denote perceptual sensations—it seems logical such a system is based on how human beings see colour,’’ The natural colour system embodies the colour theories from art, philosophy and science. Combining as it does the proposals of da Vinci (artist and scientist), Forsius (astronomer), Hering (scientist), Runge (artist), and Wittgenstein (philosopher), NCSs is a colour notation system which describes colours perceptually, based on the six elementary or pure colours, red, blue, green, yellow plus white and black. As mentioned in the introduction, NCSs describes colours in terms of their resemblance to the four chromatic elementary colours plus their relationship to the achromatic black and white. For example, in the NCSs Notation S 1050-Y90R, S designates a standard NCSs colour and 1050 the nuance of the colour, a combination of blackness and chromaticness i.e. 10 denotes a 10% visual attribute to blackness and 50 denotes a chromaticness of 50%. Fig. 11 Nuance defines the position of the colour within an NCSs (Hering) triangle of a given hue. The NCSs notation defines hue as a visual combination of two of the chromatic elementary colours from yellow in a clockwise direction through red followed by
Fig. 11. NCSs Triangle.
Fig. 12. NCSs Notation.
Fig. 13. Colour Wheels of Art and Perception (NCSs).
blue then green. In this case we have the notation Y90R a yellow with a 90% visual attribute towards redness (Fig. 12). If we now compare the colour wheels of art and perception we can see some similarities but also distinct differences (Fig. 13). Yellow through to red is the same for both wheels but opposite red in the colour wheel of art we have a green tone blue S 2555-B30G rather than the pure visual green. Opposite yellow on the colour wheel of art we have a purple with the NCSs notation S 3555-R60B not the pure visual blue of NCSs. With the exception of yellow which is visually dominant (in NCSs terminology) over an arc of 901 in both wheels the proportions of the other elementary colours when dominant are different. In NCSs, the four elementary colours are equally spaced, all covering when dominant an arc of 901 (25% of the colour wheel) e.g. for yellow from hue G50Y to Y50R and for red from hue Y50R to R50B. In art red when dominant (in NCSs terminology) covers an arc of 1001, blue an arc of 1251 and green an arc of only 451. Blue takes a much larger share of the colour wheel particularly from green, which is considered to be a secondary colour in art.
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4. The colour wheel of science Newton’s discoveries revolutionised the understanding of colour. Aristotelian and other earlier interpretations were based on the assumption that white light had to be modified to produce colours. Newton believed that colour is a sensation of the eye rather than the Aristotelian approach that colour is a property of the surface of the object. ‘‘For the Rays to speak properly are not Coloured. In them there is nothing else than a certain Power and Disposition of this or that Colour’’ In Opticks, (1660) Newton also described a colour wheel and arranged his seven primaries red, orange, yellow, green, blue, indigo and violet in the order and proportions he determined visually from his experiments. Based on additional experimentation, Newton believed his primaries could not be further optically divided, Newton [9]. From Newton’s colour wheel one can determine the purity (saturation or chromaticness) and hue of a colour (where the colour is positioned on the circumference of the colour wheel) (Fig. 14) However, the problem with Newton’s seven primaries was how to relate them to artistic practice but by the 1800s, for example, Benjamin West (President of Royal Academy around 1805 and contemporary with Goethe) had adopted Newtonian colours in his ‘ball of prismatic colour’ [10]. Newton also did not fully understand that there were two sets of primaries, the additive primaries of light plus the subtractive primaries of pigments and artists colours. It was not until the late 18th century with the work of Young, Rood, Maxwell and von Helmholtz that there was an understanding of these two sets of primary stimuli.
Fig. 14. Isaac Newton’s Colour Wheel.
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Johanne Goethe, the German poet and philosopher, was vehemently opposed to Newton’s theories and believed that science and mathematics had no role to play in the theory of colour. The theory of colours, in particular has suffered much and its progress has been incalculably retarded by having been mixed up with optics generally, a science which cannot dispense with mathematics; whereas the theory of colours, in strictness, may be investigated quite independently of optics, Goethe [11]. It was, however, to an artist, Albert Munsell, to whom the world of colour physics turned to establish a uniform three-dimensional space for instrumental colour measurement i.e. CIE L a b . CIE L a b was developed because there was a need in the commercial environment for a mathematically based colour space, uniform in terms of defining equal visual differences between two colours by their equality within this mathematical space irrespective of their position. The 1931 CIE Chromaticity Diagram was demonstrated by D. L. MacAdam by plotting ‘‘Just Noticeable Stimulus Differences’’ onto the diagram. However, such is clearly non-uniform, severely restricting its application for instrumental colour measurement and control. The diagram is also two dimensional and does not include a function for lightness. Munsell believed that five primaries, blue, green yellow red plus purple are required to create a colour space with equal visual steps in hue. His 1929 atlas (which was published posthumously) is based on 40 hues and 1500 colours. It postulates equal visual steps of not only hue but also value (lightness) and chroma (saturation or purity) which was a prerequisite for a mathematical colour difference model. In detail, Munsell’s atlas is based on his five primaries plus five intermediate hues of red-purple (RP), purpleblue (PB), blue-green (BG), green-yellow (GY) and yellow-red (YR). For each of these hue there is a set of four further hues 2.5, 5, 7.5 and 10 i.e. 2.5R, 5R, 7.5R, 10R then 2.5RP, 5RP for clockwise movement around the colour wheel. Within each hue there is a range of colours uniformly varying visually in value and chroma with a notation for value from 0 to 10 and for chroma from 0 to 12 (Fig. 15). The CIE L a b colour space, published in 1976, was based on the work of many researchers including Adams, Hunter, Judd, MacAdam, Muller, Nickerson. Billmeyer and Saltzmann [12]. The CIE L a b axes are L lightness, a the red-green opponent axis (with þa being red and a being green) and b the blue-yellow opponent axis (b is blue and þb is yellow) (Fig. 16). The rationale of CIE L a b colour space includes features of Herings’s opponent colour theory, the
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Fig. 15. Albert Munsell Colour Notation System.
Fig. 16. CIE L*a*b* Colour Space.
three-dimensionality of colour space outlined by Runge and the concept of six pure elementary colours white, black, blue, green, yellow and red as proposed by da Vinci. Furthermore CIE L a b colour space is a mathematical model for Munsell’s Atlas comprising five chromatic primaries blue, green, yellow, red and purple and two achromatic primaries black and white. If the CIE L a b colour wheel (Fig. 17) is examined immediate differences can be seen between this and the perceptual NCSs colour wheel. On the a axis the red is not the pure visual red of NCSs S 1080-R but is magenta and has the NCSs notation S 2060-R20B. The green is not the pure visual green S 1565-G but a blue tone green with the NCSs notation of S 2060-B70G. The pure visual red of NCSs is not at 01 but at 22.51 and the pure visual green not at 1801 but at 167.51. These differences rise from the objective to have a mathematical model with uniform visual colour differences. To achieve this, extra space for the fifth Munsell primary purple was required, pushing red and green upwards on the colour wheel by 22.51. On the b axis the yellow is a green tone yellow S 0575-G90Y and the blue is an ultramarine with an NCSs notation of S 2565-R80B.
Fig. 17. Colour Wheels of CIE L*a*b* and Perception (NCSs).
Is this apparent anomaly significant? Not necessarily, but a user should be aware of the model on which CIE L a b is based. This is a reflection of the fact that colour measurement is relative, and not a precise analytical tool. There is a wide range of spectrophotometers available for colour measurement, these employ varying optical geometries which impact on the CIE L a b values obtained. As long as the measurement protocol is precisely defined, excellent repeatability of measurement results can be obtained. A further comparison of the two wheels (Fig. 17) reveals the comparative proportional representation of the four chromatic elementary colours blue, green, yellow and red. As seen previously in the NCSs colour wheel, each of the elementary colours is dominant over an arc of 901. With the CIE colour wheel on the other hand, this is not the case, with blue taking space from green with an arc of 1451, green being dominant over an arc of only 451, yellow over an arc of 701 and red 1001. Blue is therefore the most dominant, followed by red at the expense of green and yellow which is a consequence of including purple as a primary. CIE L a b has an artistic background from Albert Munsell so let us now compare the colour wheels of science (CIE) and art (Fig. 18). The relative proportions of the dominant areas covered by the four elementary colours are quite similar. Blue is the most dominant at 1451 for CIE and 1251 for art, red 1001 for both wheels, yellow losing out to blue in the CIE wheel at 701 compared with 901 in the artistic wheel and green is similar with 451 arcs in both wheels. However, the positioning of the colours on the wheels is quite different with S 0575-G90Y being the yellow of CIE, the pure NCSs visual yellow S 0580-Y for art, S 2060-R20B the red for CIE with the pure visual NCSs red S 1080-R for art, the CIE blue is S 2565-R80B and the blue for art much redder with S 3555-R60B. The greens are also significantly different with S 2060-B70G for CIE and a much bluer green for art with S 2555B30G.
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Fig. 18. Colour Wheels of CIE L*a*b* and Art.
5. The colour wheel of physiology Lastly, we examine the colour wheel of physiology (after image) and the concept of complementary colours plus the phenomenon of after image. The expression ‘complementary colours’ can cause much controversy. It could be argued that it is too simplistic to state that complementary colours/stimuli are those which lie on opposite sides of a colour wheel or diagram. However, in strict terms of physics, by mixing two complementary (or additive) colours (or stimuli) their combined spectral wavelength distribution would produce white light, (or achromatic stimulus). This, then is a consistent use of the basic term complementum fill up or complete. Following the above logic the 1931 CIE chromaticity diagram with a 21 observer is a good starting point when considering the concept of complementary colours (Fig. 4). Much useful information can be obtained about a colour stimulus e.g. its excitation purity (chromaticness), dominant wavelength (hue) and complementary colour. In the example given we are using the CIE standard daylight illuminant D65, with chromaticity coordinates x ¼ 0:3127, y ¼ 0:3290 and a blue with the coordinates x ¼ 0:110, y ¼ 0:340. If a line is drawn from D65 through the chromaticity values of the colour in question to the spectral locus of the 1931 Chromaticity Diagram, the locus is dissected at 492 nm. This is the dominant wavelength or hue of the colour. If this line is then extended to the opposite side of the diagram, the spectral locus is dissected at 610 nm, giving the complementary colour which has an orange hue. In art, while the concept of complementary colours is similar the use of pigments involves subtractive colour mixing, meaning that a mix of two truly complementary colours gives a neutral grey, rather than the above white of additive colour mixing. A third set of complementary colours can be produced by the phenomenon of after image. Having observed a colour (visual stimulus), particularly a highly chromatic one, on an observer looking away from it an after image is perceived, not of the
Fig. 19. After Image.
colour itself but of what may be considered to be its complement (Fig. 19). A good understanding of the mechanism of after image and opponent processes may be obtained from Hurvich [13]. As part of the project reported here I produced a physiological colour wheel using a technique recommended by Smedal. I began with the pure NCSs visual yellow S 0580-Y. After staring at this colour for 15 s then turning away and looking at a white background, I experienced an after image of a red tone blue which I identified as S 2565-R80B. To check this assessment I placed the two colours next to each other both on a white background. After staring at these for 15 s I was able to visually drag the complementary colours away from each colour and could check this visual colour experience against the original colours.
Using this technique I developed the colour wheel of Fig. 20. Figs. 21–23 show the positioning of the complementary colours of after image on the colour wheels of art, perception and science. There appears to be little correlation between these. However, with the colour wheel of perception ðNCSsÞ, even though there is not complete synchronisation with the positioning of the after image colours, there is a distinct cross over of the complementary axes at a hue of R40B and a chromaticness of 20.
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Fig. 23. Colour Wheels of Physiology (After Image) and CIE L*a*b*.
Fig. 20. Colour Wheel of Physiology (After Image).
Fig. 21. Colour Wheels of Physiology (After Image) and Art.
Fig. 24. The Four Colour Wheels.
6. Conclusion By comparing all four colour wheels (Fig. 24) the relationship between the four elementary colours in each wheel may be clearly seen. The most striking conclusion, using NCSs nomenclature, is the dominance of blue and the converse for green in the colour wheels of art, science and physiology. This is opposite to the 1931 CIE Chromaticity diagram where green appears to be dominant. Fig. 22. Colour Wheels of Physiology (After Image) and Perception (NCSs).
A more complete colour wheel with a greater number of colours would be beneficial to the overall analysis of the physiological colour wheel.
Discipline
Blue
Green
Yellow
Red
Art Science CIE Perception NCSs Physiology after image
1251 1451 901 1351
451 451 901 451
901 701 901 901
1001 1001 901 901
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Red is similarly (within 101) represented in all wheels as is yellow with the exception of the colour wheel of science (CIE). This project focuses on colour perception in that it was intended solely as one of observation and comparison. No one perfect or ideal colour wheel could be identified and all of the colour wheels reviewed has support from both theory and practice. The important issue is the necessity for awareness and understanding of the different philosophies behind each wheel and an acceptance of their own well established and proven individual application.
References [1] Gage J. Colour and culture, practice and meaning from antiquity to abstraction. London: Thames & Hudson; 1993. [2] Anders H, Gunnar SLT. NCS natural color system—from concept to research and applications. Parts 1 and 2, Color research and application 1996. CCC 0361-2317/96/030180-26 and CCC 0361-2317/96/030206-15. Wiley.
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[3] Hering E. English Translation by Hurvich Leo M. and Jameson Dorothea: Outlines of a Theory of the light sense. Cambridge: Harvard University Press; 1964. [4] Boyle R. Experiments & considerations touching colours 1664, p. 219–21: Gage John, Colourand Culture, P36, Thames and Hudson, 1993, Cambridge. [5] Itten J. The elements of color, vol. 31. New York: van Nostrand Reinhold; 1970. [6] Wittgenstein L. Remarks on colour, vol. 158/38e. Oxford: Basil Blackwell; 1977. [7] Kemp M. The science of art. Yale: Yale University Press; 1990, p. 268. [8] Forsius Sigfrid Aron, Physica, Handwritten Manuscript, Stockholm 1611. [9] Newton I, 1730. Opticks. New York: Dover Publications; 1952. [10] Brunelleschi to Seurat. New Haven & London: Yale University Press; 1990. [11] Goethe JQ. Theory of colours, vol. 287, translated by Charles Lock Eastlake. Cambridge, MA: MIT Press; 1970. [12] Billmeyer F, Saltzman M. Principles of color technology. 3rd ed. Berns RS, editor. New York: Wiley; 2000. [13] Hurvich Leo M, Color vision. Opponent processes and electrophysiology. Sinauer Associates Inc. Sunderland, Massachusetts, 1981. [chapter 12].
Optics & Laser Technology 38 (2006) 219–229 www.elsevier.com/locate/optlastec
The colour wheels of art, perception, science and physiology Nick Harkness,1 Nick Harkness Pty Ltd., Birdcage 3.1, 65 Doody Street, South Sydney Corporate Park, Alexandria NSW 2015, Australia Available online 15 August 2005
Abstract Colour is not the domain of any one discipline be it art, philosophy, psychology or science. Each discipline has its own colour wheel and this presentation examines the origins and philosophies behind the colour circles of Art, Perception, Science and Physiology (after image) with reference to Aristotle, Robert Boyle, Leonardo da Vinci, Goethe, Ewald Hering and Albert Munsell. The paper analyses and discusses the differences between the four colour wheels using the Natural Colour Systems notation as the reference for hue (the position of colours within each of the colour wheels). Examination of the colour wheels shows the dominance of blue in the wheels of art, science and physiology particularly at the expense of green. This paper does not consider the three-dimensionality of colour space its goal was to review the hue of a colour with regard to its position on the respective colour wheels. r 2005 Elsevier Ltd. All rights reserved. Keywords: CIE L a b ; Colour circles; Colour wheels; Elementary colours; Primary colours; The Natural Colour Systems; The Munsell system
1. Introduction In June 2003 I attended a 5-day residential Colour Summer School run by the Scandinavian Colour Institute at Gripsho¨lm, near Stockholm, Sweden. Out of the 22 attendees only one (myself) was scientifically trained the rest being from non-scientific design or art backgrounds. The course leaders were the international colour educators Berit Bergstro¨m, Chief Executive Officer, Scandinavian Colour School, and Professor Grete Smedal, University of Bergen, Norway. With my background in instrumental colour measurement, this became a trans-disciplinary experience for me, including mixing artist colours, exercises on colour memory, colour combinations and simultaneous contrast.
Corresponding author. Tel.: +61 2 9700 8110; 61 2 9700 8112.
E-mail address: [email protected]. Also at: Chair, Colour Society of Australia Organising Committee for International Colour Association Congress 2009, Sydney. 1
0030-3992/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2005.06.010
The paper reports the results of my project, an examination of the colour wheels of art, perception, science and physiology. The preoccupation with colour wheels or circles is intriguing, the rainbow is a bow but within the bow the colours, running from red to violet, are each a continuum and show linearity across the bow (Fig. 1). The rainbow can also form a circle when viewed from an aircraft and Scheuchzer 1731 observed their circularity, i.e. when looking down on a waterfall [1]. Within these circles the colours are again a continuum and exhibit linearity along the radii. Similarly, a scientific (physics) interpretation of the visible spectrum of daylight also gives linearity from blue to red. The visible wavelength range, nominally spans between 400 and 700 nm. Below 400 nm is ultraviolet radiation which we (subjectively) cannot see but can feel through sunburn and above 700 nm there is infra-red radiation which again is invisible but warming. The spectrum is non-circular (Fig. 2). To seek a solution to this possible enigma requires a study of the mechanism of colour vision and the spectral
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Fig. 3. CIE 1931 2 colour matching functions x¯ l y¯ l z¯ l . Fig. 1. Rainbow (do you have a better image on file?).
Fig. 2. Spectral Power Distribution CIE Illuminant D65.
sensitivity of the cones which provide us with colour vision. Examination of the CIE (the International Commission on Illumination) 1931 21 colour matching functions x¯ l , y¯ l & z¯ l reveals distinct peaks for the spectral sensitivity of both the medium wavelength cone y¯ l (green) at 555 nm and the short wave length cone z¯ l (blue) at 445 nm. The long wave length cone x¯ l (red), however, has two peaks, at 600 nm (primary) and 440 nm (secondary) lying below the peak for the short wave length cone (Fig. 3). The CIE 1931 x, y Chromaticity diagram (Fig. 4) was derived from these colour matching functions and the two ends of the spectral locus are joined together, completing the ‘‘circle’’ with the non-spectral colours which are mixtures of long and short wavelength light which we perceive as mixtures of blue and red. A combination of the primary peak sensitivity of the short
wavelength cone (blue) and the secondary peak of the long wavelength cone (red). In this examination of the colour wheels the NCSs colour notation system has been used as the reference for hue, (where hue is a colour’s position on a colour wheel) [2]. NCSs notation describes a colour’s hue in terms of a visual combination of the four chromatic colours we imagine to be pure colours i.e. blue, green, red, and yellow. NCSs notation defines four quadrants based on combinations of two of these four ‘‘pure’’ colours, giving yellow-red, red-blue, blue-green and greenyellow. Examples are Y40R a yellow with a 40% visual attribute towards redness and G60Y a green with a 60% visual attribute towards yellowness. NCSs notation provides a very suitable reference for comparing the configuration of hues on the different wheels, originating from the work based on a perceptual point of view initiated by Ewald Hering [3] .This is based on the concept that we perceive six pure or elementary colours, namely the achromatic white, and black and the chromatic blue, green, red, and yellow. Any colour can be described in terms of its visual relationship to a combination of a number of these six ‘‘pure’’ colours but as explained later there cannot be a relationship which includes yellow and blue together nor red and green. NCSs notation characterizes colours and differences between colours perceptually. Among Hering’s goals was: ‘‘in any event we would have a quantitative comparison of colour differences only, and not a measure of colour itself’’ [3].
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Fig. 4. CIE 1931 Chromaticity Diagram.
2. The colour wheel of art In the context of art, the Irish physicist Robert Boyle proposed: ‘‘There are but few Simple and Primary colours (if I may so call them) from whose various compositions all the rest do as it were result. For though painters can imitate the Hues (though not always the splendour) of those numberless differing colours that are to be met with in the works of nature, and of art, I have not yet found, that to exhibit this strange Variety they need imploy any more than white and black, and red, and blue and yellow and these variously compounded, and (if I may so speak) decompounded, being sufficient to exhibit a variety and number of colours’’ [4]. We first consider then the context of art and design. This uses the classic Johanne Itten [5], colour wheel based on the three primaries of art red, yellow and blue (Fig. 5), as taught in primary school. To produce my first colour wheel I selected gouache paints yellow (process), red (vermilion) and blue (cobalt blue). (It should be noted that the artist does have a palette from which a multitude of blues, reds and yellows and combinations can be selected to develop an artistic colour wheel). My selection resulted not in the expected colour wheel of Johannes Itten, but a beautiful chromatic and dynamic orange, then a purple—a mud colour would be a better description—and a green closer to khaki. (Fig. 6) This necessitated a revisit of the primary colours. There are two sets of primaries depending on whether
Fig. 5. Johannes Itten Colour Wheel.
the colour mixing is additive or subtractive. In the first case we have, red, green and blue, which are the primaries of light, used for example in television and computer monitors. H.G. Grassman (1853), whose laws form the basis of modern colorimetry, stated that each of the three additive primary colours cannot be made by a mixture of the other two primaries (or a mixture of other colours). For example purple is a reddish blue or a bluish red and orange is a yellowish red or a reddish
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Fig. 8. Subtractive Primaries.
Fig. 6. Colour Wheel of ‘‘Art’’ 1.
and mixing these together tends towards blackness, more light being absorbed (or subtracted) as more pigments are added. (Fig. 8) The secondaries of additive colour mixing (yellow, magenta and cyan) can be considered to be the true primaries of subtractive colour mixing, rather than red, yellow and blue. As stated above the artist has an extensive palette from which to select a red (bluish or yellowish), yellow (greenish or reddish) and blue (greenish or reddish). An artist may describe yellow, magenta and cyan as the ‘‘process’’ primaries (together with black) rather than being the ‘‘traditional’’ primaries of art. Likewise red, blue and green can be considered to be the true secondaries of subtractive mixing and not orange, purple and green. For my second attempt process yellow, magenta (a bluish red) and cyan (to me similar in colour to the pure visual blue of NCSs were selected, and as shown in (Fig. 9) even with my limited artistic skills to ‘‘my perception’’ a ‘‘perfect’’ colour wheel was produced.
Fig. 7. Additive Primaries.
3. The colour wheel of perception yellow. Red, however, cannot be a purplish orange or an orange purple. Combining red, green and blue light results in white light. The secondaries of additive colour mixing are yellow (green light plus red light), cyan (blue plus green) and magenta (blue plus red) (Fig. 7). The primaries of light are also the primaries of vision as noted above. We typically refer to the short, medium and long wave length cones as the blue, green and red cones. This description was first used by Thomas Young and Herman Ludwig Ferdinand von Helmholtz. Subtractive colour mixing, on the other hand refers to mixtures of pigments and dyestuffs which absorb light
It has already been noted that with visual colour perception rather than three primaries six pure or elementary colours are used, white, black, red, green, yellow and blue. It might be thought to be wrong to include green as it is considered to be a mixture between blue and yellow. However, while a yellowish red or yellowish green are possible, perception does not allow a bluish yellow nor a yellowish blue. In fact, a pure green is possible which has neither a ‘bluishness’ nor ‘yellowishness’. Wittgenstein [6]. As far back as circa 1480 Leonardo da Vinci, in his ‘‘Treatise on Painting’’ circa 1480, argued that there were six elementary colours;
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Fig. 10. Aron Sigfrid Forsius 1603, Physica Manuskripts 1611.
Fig. 9. Colour Wheel of ‘‘Art’’ 2.
‘‘The first of all simple colours is white, though philosophers will not acknowledge either white or black to be colours; because the first is the cause, or the receiver of colours and the other totally deprived of them. But as painters cannot do without either, we shall place them among the others; and according to this order of things, white will be the first, yellow the second, green the third, blue the fourth, red the fifth, and black the six. We shall set down white for the representative of light, without which no colour can be seen; yellow for earth; green for water, blue for air, red for fire; and black for total darkness’’ Kemp [7]
contribute to our current understanding of the mechanism of colour vision, namely Young and Helmholtz at the first stage of the colour vision process—the cone level—and Hering at the second or perceptual stage. Hering also defined a colour triangle [3]: If we imagine a clear red of a specific hue placed at one corner (r) of a triangle, a completely pure white at the second corner (w), and a completely pure black at the third corner (b) then all possible transitions from clear red to pure white can be arranged along the line (r) to (w), and all transitions between clear red and pure black along the line connecting (r) and (b). As the distance from clear red increases, the colors thus ordered would be continuously more veiled by white on one side and by black on the other until finally all trace of redness vanished in pure white or black .
In his Physica Manuskript (1611) [8], Aron Sigfrid Forsius, Professor of Astronomy in Uppsala, Sweden also referred to these six elementary colours: ‘‘among the colours there are two basic colours white and black . . .. the four intermediate colours are red, blue, green and yellow—and grey from white to black—and these increase in intensity by degrees. . . changing from white by paling or to black by darkening’’. Professor Forsius arranged these six elementary colours and their mixtures in what appears to be a twodimensional diagram. (Fig. 10). In 1878, the psychologist Ewald Hering proposed his opponent colour theory of colour vision based on four psychological primaries: red, green, yellow and blue, where red—green and yellow— blue have a postulated opponent psychological relationship. Hering’s hypothesis appears initially to be in conflict with those of Thomas Young and Helmholtz which are based on the three primaries of colour vision: red, green and blue. Both the latter are in fact partially correct and
(w)
(r)
(b)
Hering’s triangles, which rotate over all hues with the achromatic axis at the centre, make an important contribution to the concept of the three-dimensionality of colour space.
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Philipp Otto Runge’s (1810) design of a colour solid was similarly related to three-dimensional colour space. This was a sphere based on the tints (reductions of the pure colour with white), tones (reductions with grey) and shades (reductions with black). In 1979, the Swedish researchers Anders Ha˚rd, Gunnar Tonnquist and Lars Sivik introduced the Natural Colour Systems. The rationale was stated by Tonnquist (Scandinavian Colour Institute): ‘‘As a system in first hand shall denote perceptual sensations—it seems logical such a system is based on how human beings see colour,’’ The natural colour system embodies the colour theories from art, philosophy and science. Combining as it does the proposals of da Vinci (artist and scientist), Forsius (astronomer), Hering (scientist), Runge (artist), and Wittgenstein (philosopher), NCSs is a colour notation system which describes colours perceptually, based on the six elementary or pure colours, red, blue, green, yellow plus white and black. As mentioned in the introduction, NCSs describes colours in terms of their resemblance to the four chromatic elementary colours plus their relationship to the achromatic black and white. For example, in the NCSs Notation S 1050-Y90R, S designates a standard NCSs colour and 1050 the nuance of the colour, a combination of blackness and chromaticness i.e. 10 denotes a 10% visual attribute to blackness and 50 denotes a chromaticness of 50%. Fig. 11 Nuance defines the position of the colour within an NCSs (Hering) triangle of a given hue. The NCSs notation defines hue as a visual combination of two of the chromatic elementary colours from yellow in a clockwise direction through red followed by
Fig. 11. NCSs Triangle.
Fig. 12. NCSs Notation.
Fig. 13. Colour Wheels of Art and Perception (NCSs).
blue then green. In this case we have the notation Y90R a yellow with a 90% visual attribute towards redness (Fig. 12). If we now compare the colour wheels of art and perception we can see some similarities but also distinct differences (Fig. 13). Yellow through to red is the same for both wheels but opposite red in the colour wheel of art we have a green tone blue S 2555-B30G rather than the pure visual green. Opposite yellow on the colour wheel of art we have a purple with the NCSs notation S 3555-R60B not the pure visual blue of NCSs. With the exception of yellow which is visually dominant (in NCSs terminology) over an arc of 901 in both wheels the proportions of the other elementary colours when dominant are different. In NCSs, the four elementary colours are equally spaced, all covering when dominant an arc of 901 (25% of the colour wheel) e.g. for yellow from hue G50Y to Y50R and for red from hue Y50R to R50B. In art red when dominant (in NCSs terminology) covers an arc of 1001, blue an arc of 1251 and green an arc of only 451. Blue takes a much larger share of the colour wheel particularly from green, which is considered to be a secondary colour in art.
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4. The colour wheel of science Newton’s discoveries revolutionised the understanding of colour. Aristotelian and other earlier interpretations were based on the assumption that white light had to be modified to produce colours. Newton believed that colour is a sensation of the eye rather than the Aristotelian approach that colour is a property of the surface of the object. ‘‘For the Rays to speak properly are not Coloured. In them there is nothing else than a certain Power and Disposition of this or that Colour’’ In Opticks, (1660) Newton also described a colour wheel and arranged his seven primaries red, orange, yellow, green, blue, indigo and violet in the order and proportions he determined visually from his experiments. Based on additional experimentation, Newton believed his primaries could not be further optically divided, Newton [9]. From Newton’s colour wheel one can determine the purity (saturation or chromaticness) and hue of a colour (where the colour is positioned on the circumference of the colour wheel) (Fig. 14) However, the problem with Newton’s seven primaries was how to relate them to artistic practice but by the 1800s, for example, Benjamin West (President of Royal Academy around 1805 and contemporary with Goethe) had adopted Newtonian colours in his ‘ball of prismatic colour’ [10]. Newton also did not fully understand that there were two sets of primaries, the additive primaries of light plus the subtractive primaries of pigments and artists colours. It was not until the late 18th century with the work of Young, Rood, Maxwell and von Helmholtz that there was an understanding of these two sets of primary stimuli.
Fig. 14. Isaac Newton’s Colour Wheel.
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Johanne Goethe, the German poet and philosopher, was vehemently opposed to Newton’s theories and believed that science and mathematics had no role to play in the theory of colour. The theory of colours, in particular has suffered much and its progress has been incalculably retarded by having been mixed up with optics generally, a science which cannot dispense with mathematics; whereas the theory of colours, in strictness, may be investigated quite independently of optics, Goethe [11]. It was, however, to an artist, Albert Munsell, to whom the world of colour physics turned to establish a uniform three-dimensional space for instrumental colour measurement i.e. CIE L a b . CIE L a b was developed because there was a need in the commercial environment for a mathematically based colour space, uniform in terms of defining equal visual differences between two colours by their equality within this mathematical space irrespective of their position. The 1931 CIE Chromaticity Diagram was demonstrated by D. L. MacAdam by plotting ‘‘Just Noticeable Stimulus Differences’’ onto the diagram. However, such is clearly non-uniform, severely restricting its application for instrumental colour measurement and control. The diagram is also two dimensional and does not include a function for lightness. Munsell believed that five primaries, blue, green yellow red plus purple are required to create a colour space with equal visual steps in hue. His 1929 atlas (which was published posthumously) is based on 40 hues and 1500 colours. It postulates equal visual steps of not only hue but also value (lightness) and chroma (saturation or purity) which was a prerequisite for a mathematical colour difference model. In detail, Munsell’s atlas is based on his five primaries plus five intermediate hues of red-purple (RP), purpleblue (PB), blue-green (BG), green-yellow (GY) and yellow-red (YR). For each of these hue there is a set of four further hues 2.5, 5, 7.5 and 10 i.e. 2.5R, 5R, 7.5R, 10R then 2.5RP, 5RP for clockwise movement around the colour wheel. Within each hue there is a range of colours uniformly varying visually in value and chroma with a notation for value from 0 to 10 and for chroma from 0 to 12 (Fig. 15). The CIE L a b colour space, published in 1976, was based on the work of many researchers including Adams, Hunter, Judd, MacAdam, Muller, Nickerson. Billmeyer and Saltzmann [12]. The CIE L a b axes are L lightness, a the red-green opponent axis (with þa being red and a being green) and b the blue-yellow opponent axis (b is blue and þb is yellow) (Fig. 16). The rationale of CIE L a b colour space includes features of Herings’s opponent colour theory, the
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Fig. 15. Albert Munsell Colour Notation System.
Fig. 16. CIE L*a*b* Colour Space.
three-dimensionality of colour space outlined by Runge and the concept of six pure elementary colours white, black, blue, green, yellow and red as proposed by da Vinci. Furthermore CIE L a b colour space is a mathematical model for Munsell’s Atlas comprising five chromatic primaries blue, green, yellow, red and purple and two achromatic primaries black and white. If the CIE L a b colour wheel (Fig. 17) is examined immediate differences can be seen between this and the perceptual NCSs colour wheel. On the a axis the red is not the pure visual red of NCSs S 1080-R but is magenta and has the NCSs notation S 2060-R20B. The green is not the pure visual green S 1565-G but a blue tone green with the NCSs notation of S 2060-B70G. The pure visual red of NCSs is not at 01 but at 22.51 and the pure visual green not at 1801 but at 167.51. These differences rise from the objective to have a mathematical model with uniform visual colour differences. To achieve this, extra space for the fifth Munsell primary purple was required, pushing red and green upwards on the colour wheel by 22.51. On the b axis the yellow is a green tone yellow S 0575-G90Y and the blue is an ultramarine with an NCSs notation of S 2565-R80B.
Fig. 17. Colour Wheels of CIE L*a*b* and Perception (NCSs).
Is this apparent anomaly significant? Not necessarily, but a user should be aware of the model on which CIE L a b is based. This is a reflection of the fact that colour measurement is relative, and not a precise analytical tool. There is a wide range of spectrophotometers available for colour measurement, these employ varying optical geometries which impact on the CIE L a b values obtained. As long as the measurement protocol is precisely defined, excellent repeatability of measurement results can be obtained. A further comparison of the two wheels (Fig. 17) reveals the comparative proportional representation of the four chromatic elementary colours blue, green, yellow and red. As seen previously in the NCSs colour wheel, each of the elementary colours is dominant over an arc of 901. With the CIE colour wheel on the other hand, this is not the case, with blue taking space from green with an arc of 1451, green being dominant over an arc of only 451, yellow over an arc of 701 and red 1001. Blue is therefore the most dominant, followed by red at the expense of green and yellow which is a consequence of including purple as a primary. CIE L a b has an artistic background from Albert Munsell so let us now compare the colour wheels of science (CIE) and art (Fig. 18). The relative proportions of the dominant areas covered by the four elementary colours are quite similar. Blue is the most dominant at 1451 for CIE and 1251 for art, red 1001 for both wheels, yellow losing out to blue in the CIE wheel at 701 compared with 901 in the artistic wheel and green is similar with 451 arcs in both wheels. However, the positioning of the colours on the wheels is quite different with S 0575-G90Y being the yellow of CIE, the pure NCSs visual yellow S 0580-Y for art, S 2060-R20B the red for CIE with the pure visual NCSs red S 1080-R for art, the CIE blue is S 2565-R80B and the blue for art much redder with S 3555-R60B. The greens are also significantly different with S 2060-B70G for CIE and a much bluer green for art with S 2555B30G.
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Fig. 18. Colour Wheels of CIE L*a*b* and Art.
5. The colour wheel of physiology Lastly, we examine the colour wheel of physiology (after image) and the concept of complementary colours plus the phenomenon of after image. The expression ‘complementary colours’ can cause much controversy. It could be argued that it is too simplistic to state that complementary colours/stimuli are those which lie on opposite sides of a colour wheel or diagram. However, in strict terms of physics, by mixing two complementary (or additive) colours (or stimuli) their combined spectral wavelength distribution would produce white light, (or achromatic stimulus). This, then is a consistent use of the basic term complementum fill up or complete. Following the above logic the 1931 CIE chromaticity diagram with a 21 observer is a good starting point when considering the concept of complementary colours (Fig. 4). Much useful information can be obtained about a colour stimulus e.g. its excitation purity (chromaticness), dominant wavelength (hue) and complementary colour. In the example given we are using the CIE standard daylight illuminant D65, with chromaticity coordinates x ¼ 0:3127, y ¼ 0:3290 and a blue with the coordinates x ¼ 0:110, y ¼ 0:340. If a line is drawn from D65 through the chromaticity values of the colour in question to the spectral locus of the 1931 Chromaticity Diagram, the locus is dissected at 492 nm. This is the dominant wavelength or hue of the colour. If this line is then extended to the opposite side of the diagram, the spectral locus is dissected at 610 nm, giving the complementary colour which has an orange hue. In art, while the concept of complementary colours is similar the use of pigments involves subtractive colour mixing, meaning that a mix of two truly complementary colours gives a neutral grey, rather than the above white of additive colour mixing. A third set of complementary colours can be produced by the phenomenon of after image. Having observed a colour (visual stimulus), particularly a highly chromatic one, on an observer looking away from it an after image is perceived, not of the
Fig. 19. After Image.
colour itself but of what may be considered to be its complement (Fig. 19). A good understanding of the mechanism of after image and opponent processes may be obtained from Hurvich [13]. As part of the project reported here I produced a physiological colour wheel using a technique recommended by Smedal. I began with the pure NCSs visual yellow S 0580-Y. After staring at this colour for 15 s then turning away and looking at a white background, I experienced an after image of a red tone blue which I identified as S 2565-R80B. To check this assessment I placed the two colours next to each other both on a white background. After staring at these for 15 s I was able to visually drag the complementary colours away from each colour and could check this visual colour experience against the original colours.
Using this technique I developed the colour wheel of Fig. 20. Figs. 21–23 show the positioning of the complementary colours of after image on the colour wheels of art, perception and science. There appears to be little correlation between these. However, with the colour wheel of perception ðNCSsÞ, even though there is not complete synchronisation with the positioning of the after image colours, there is a distinct cross over of the complementary axes at a hue of R40B and a chromaticness of 20.
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Fig. 23. Colour Wheels of Physiology (After Image) and CIE L*a*b*.
Fig. 20. Colour Wheel of Physiology (After Image).
Fig. 21. Colour Wheels of Physiology (After Image) and Art.
Fig. 24. The Four Colour Wheels.
6. Conclusion By comparing all four colour wheels (Fig. 24) the relationship between the four elementary colours in each wheel may be clearly seen. The most striking conclusion, using NCSs nomenclature, is the dominance of blue and the converse for green in the colour wheels of art, science and physiology. This is opposite to the 1931 CIE Chromaticity diagram where green appears to be dominant. Fig. 22. Colour Wheels of Physiology (After Image) and Perception (NCSs).
A more complete colour wheel with a greater number of colours would be beneficial to the overall analysis of the physiological colour wheel.
Discipline
Blue
Green
Yellow
Red
Art Science CIE Perception NCSs Physiology after image
1251 1451 901 1351
451 451 901 451
901 701 901 901
1001 1001 901 901
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Red is similarly (within 101) represented in all wheels as is yellow with the exception of the colour wheel of science (CIE). This project focuses on colour perception in that it was intended solely as one of observation and comparison. No one perfect or ideal colour wheel could be identified and all of the colour wheels reviewed has support from both theory and practice. The important issue is the necessity for awareness and understanding of the different philosophies behind each wheel and an acceptance of their own well established and proven individual application.
References [1] Gage J. Colour and culture, practice and meaning from antiquity to abstraction. London: Thames & Hudson; 1993. [2] Anders H, Gunnar SLT. NCS natural color system—from concept to research and applications. Parts 1 and 2, Color research and application 1996. CCC 0361-2317/96/030180-26 and CCC 0361-2317/96/030206-15. Wiley.
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[3] Hering E. English Translation by Hurvich Leo M. and Jameson Dorothea: Outlines of a Theory of the light sense. Cambridge: Harvard University Press; 1964. [4] Boyle R. Experiments & considerations touching colours 1664, p. 219–21: Gage John, Colourand Culture, P36, Thames and Hudson, 1993, Cambridge. [5] Itten J. The elements of color, vol. 31. New York: van Nostrand Reinhold; 1970. [6] Wittgenstein L. Remarks on colour, vol. 158/38e. Oxford: Basil Blackwell; 1977. [7] Kemp M. The science of art. Yale: Yale University Press; 1990, p. 268. [8] Forsius Sigfrid Aron, Physica, Handwritten Manuscript, Stockholm 1611. [9] Newton I, 1730. Opticks. New York: Dover Publications; 1952. [10] Brunelleschi to Seurat. New Haven & London: Yale University Press; 1990. [11] Goethe JQ. Theory of colours, vol. 287, translated by Charles Lock Eastlake. Cambridge, MA: MIT Press; 1970. [12] Billmeyer F, Saltzman M. Principles of color technology. 3rd ed. Berns RS, editor. New York: Wiley; 2000. [13] Hurvich Leo M, Color vision. Opponent processes and electrophysiology. Sinauer Associates Inc. Sunderland, Massachusetts, 1981. [chapter 12].