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I’m undertaking a PhD in colour perception in the School of Art and Design at Cardiff Metropolitan University. Here’s the skinny…

Deep Colour

How colour aids our perception of depth and space

Research into colour tends to be grounded in either the phenomenological or the ontological[i]. That is, colour theories either seek to model the experience of colour, or instead to explain the physics of colour and the behaviour of visible light. The European colour standards body, the International Commission on Illumination[ii] (CIE, 1932) makes this clear with a critical distinction in its influential dictionary of colour terms:

  • Perceived colour: the characteristic of visual perception that can be described by attributes of hue, brightness (or lightness) and colourfulness (or saturation or chroma); and
  • Psychophysical colour: the specification of a colour stimulus in terms of operationally defined values, such as the three tristimulus values[iii].

But to really understand the way in which colour behaves, we need to acknowledge that our experience of colour is one of both perception (how we see, understand and respond to colour); and simultaneously of the physical nature of light. To examine one without considering the other may be revealing in its own right but to understand perception at a human level, we need to explore both these dimensions concurrently.

In the visual arts, several colour models exist as frameworks to assist artists choose and use colour in their work: the highly influential Munsell Color System (Munsell, 1916) and the Swedish Natural Colour System (Hård & Sivik, 1981) for example. Many more are available for graphic artists, designers and photographers who benefit from the ubiquity of computer software such as Adobe Photoshop and Illustrator, as well as the explosion in interest and availability of computer imagery in general.[iv]

There is far less written, however, about how colour behaves in 3-dimensional spaces. Artists have some rules of thumb at their disposal: chroma and value tend to diminish with distance; distant landscapes tend towards blues and violets (Hannah, 1990), but this is hardly scientific… At the cosmological level we know that a star’s colour can tell us about its distance from earth but this has more to do with phase-shifting and the ‘Doppler Effect’ than visual perception as we typically understand it.

Here on earth, there appears to be relatively little research into how, precisely, our perception of colour is affected by distance. Similarly, I am not aware of a mathematical or quantitative model which could be used to measure depth as a result of perceived attributes of colour.

The proposed research then takes this premise as a starting point and asks the question: 

What is the role of colour in our comprehension of depth and space?

A thorough investigation of this question could lead to the creation of a theoretical model which could allow us to map and thus manipulate attributes of light and colour to permit a more intelligent reproduction of three-dimensional spaces.

Review of Literature

Chromostereopsis

Perhaps a starting point for research into depth from an optical point of view could come from the phenomena of chromostereopsis: the illusion that red and blue hues are perceived as spatially distinct due to an optical anomaly known as ‘transverse chromatic aberration’ or the distortion of certain light frequencies in the spatial plane which give rise to a feeling of greater or lesser distance.[v] (Faubert, 1994)

The phenomena is well documented in the optical sciences (Allen & Rubin, 1981; Thompson, May, & Stone, 1993) and earlier by Nobel Laureate, Willem Einthoven (Snellen, 1995).[vi] Interestingly, the phenomena rarely appears in literature originating in the visual arts.

Colour Depth

Some work at the University of Washington (Bailey, Grimm, & Davoli, 2006) investigated the role of colour as a depth cue using an easily recognisable object[vii] observed under differing lighting conditions. The authors observed a demonstrable relationship between ‘warm’ and ‘cool’ colours in determining depth, concluding that colour becomes more (or less) relevant according to the complexity of the object and the proximity to other objects.

There is a considerable amount of work done by psychologists investigating the role of colour in depth perception. Sundet (1978) provides a good roundup of this work in a historical context. A further examination of this research will be undertaken in developing the methodology outlined above.

Colour and Fine Art

Considerable writing exists as popular guides for artists in the use of colour in paintings – to convey depth or otherwise. Much of this is in the public domain in the form of texts in art schools or instructional videos on YouTube but some of which manifests in academic texts (Barrett & Bolt, 2007).

Of particular interest to this paper is the work of Dr David Briggs (2007) from the Julian Ashton Art School and the National Art School in Sydney. Briggs is also the chair of the NSW Division of the Colour Society of Australia. A great deal of his research and pedagogy from a long career in fine art education is presented on his website (Briggs, 2007).

Jan Koenderink’s paper on Colour in Artistic Intuition & Practice (2018) has also been influential in developing this proposal, exploring as it does this relatively undocumented nexus between intuitive practice in the fine arts and that of optical and neurological science.

Traditional Colour Theory

There is much to draw on in terms of theories of colour and light perception from early modernist thought to the present. Isaac Newton’s colour theories of course (1704) – flawed but incredibly influential to this day – but also those of Wilhelm Ostwald (1926), the poet Goethe (1801) and, critically, the work of Munsell (1916) whose ideas about colour, colour notation and organisation continue to dominate the modelling of colour in the digital age.

Some of this theory has informed this proposal as it stands but a more detailed study would assist the historical survey as outlined above.

Methodology

Historical Analysis

There are long traditions in the visual arts, specifically in painting, where colour is used to convey a sense of depth for the viewer. The renaissance artists of the 15th century are usually given credit for introducing linear perspective to fine art (King, 2000) [viii] but colour as an indicator of tone, mood, space and depth can be traced back well before that, certainly to the early traditions of European art (Gardner, De la Croix, & Tansey, 1975).

I will research and report on the way in which colour has been used to create a subjective sense of depth in the visual arts from early, pre-renaissance painting to the modernists of impressionism and post-impressionism and on to the digital world of today.

From this I will develop one or more hypotheses as to how and why such techniques have been used and to what extent they have been successful. For example, I hypothesis that popular notions such as ‘warm colours advance and cool recede’ may prove incorrect, or at least, not entirely correct, when subject to empirical scrutiny. Furthermore I hypothesise that colour depth is more complex than merely the apparent reduction in chroma or the shift towards blue hues which are often described in visual arts education (Hannah, 1990).

I will test these hypotheses using the following methods.

Quantitative Survey

A group of participants is organised of sufficient number to indicate a wider trend. The group is controlled for visual anomalies and otherwise normalised across age, education and, critically, visual sophistication. That is, there should be no bias, positively or negatively, towards those with a background in the visual arts.

The group is shown a range of images whose colour properties have been altered along various axes and participants are asked to identify which images (or objects within the image) convey the greatest sense of depth and in which way. Objects within each scene could be varied in terms of hue, saturation (chroma) and value (lightness).

The experiment could be conducted in a similar way to that of an optician’s test for visual anomalies, albeit without the need for expensive equipment. Indeed, it may be possible to conduct the test online which could open the possibility of a much larger sample size, particularly if some incentive could be devised which would not otherwise distort the results or skew the sample towards one group or another.

Conclusions

There is no shortage of literature on colour as an optical, neurological or psychophysical phenomenon. There is a rich tradition of education in the visual arts as to the use of colour to convey depth. There is some investigation into chromostereopsis and similar visual anomolies which give rise to a sense of depth through colour disparity. But I can discern relatively little, if any, research which specifically investigates a tangible, mathematical relationship between our human perception of colour and the degree to which that perception conveys a sense of depth in a scene – either in the ‘real world’, in the reproduction of scenes through optical means (photography or videography), or by way of synthetic modelling such as animation, 3-D modelling or visual effects.

With this in mind, I can be confident that the proposed research would be relatively unique and could contribute significantly to the creation of synthetic 3-dimensional spatial projections for use in a wide range of applications. That is, a definitive mathematical model could be developed from the results of this research which could allow optical systems to use colour properties rather than purely geometry to create more compelling and revealing 3D projections.

Bibliography

Allen, R. C., & Rubin, M. L. (1981). Chromostereopsis. Survey of Ophthalmology, 26(1), 22–27. https://doi.org/10.1016/0039-6257(81)90121-1

Bailey, R., Grimm, C., & Davoli, C. (2006). The Effect of Warm and Cool Object Colors on Depth Ordering. In ACM SIGGRAPH 2006 Research posters on – SIGGRAPH ’06 (p. 195). New York, New York, USA: ACM Press. https://doi.org/10.1145/1179622.1179845

Barrett, E., & Bolt, B. (2007). Practice as Research: Approaches to Creative Arts Enquiry. Melbourne.

Briggs, D. (2007). The Dimensions of Colour, modern colour theory. Retrieved June 7, 2018, from http://www.huevaluechroma.com/

CIE. (1932). Commission internationale de l’Eclairage proceedings, 1931. Cambridge: Cambridge University Press.

Faubert, J. (1994). Seeing depth in colour: More than just what meets the eyes. Vision Research, 34(9), 1165–1186. https://doi.org/10.1016/0042-6989(94)90299-2

Gardner, H., De la Croix, H., & Tansey, R. G. (1975). Gardner’s Art Though the Ages. Harcourt Brace Jovanovich.

Goethe, J. W. von. (1801). Zur Farbenlehre. Sämtliche Werke – Münchner Ausgabe.

Hannah, J. (1990). Artist’s Experiments with Color Perception. In M. H. Brill (Ed.) (Vol. 1250, pp. 212–219). International Society for Optics and Photonics. https://doi.org/10.1117/12.19713

Hård, A., & Sivik, L. (1981). NCS—Natural Color System: A Swedish Standard for Coloer Notation. Color Research & Application, 6(3), 129–138. https://doi.org/10.1002/col.5080060303

King, R. (2000). Brunelleschi’s dome : how a Renaissance genius reinvented architecture. New York: Walker & Co. Retrieved from https://books.google.com/books?id=JfcMAAAAQBAJ&printsec=frontcover

Koenderink, J., & van Doorn, A. (2018). Colour in Artistic Intuition & Practice.

Kuehni, R. G. (1998). Hue uniformity and the CIELAB space and color difference formula. Color Research & Application, 23(5), 314–322. https://doi.org/10.1002/(SICI)1520-6378(199810)23:5<314::AID-COL7>3.0.CO;2-Z

Luo, M. R., & Pointer, M. (2018). CIE colour appearance models: A current perspective. Lighting Research & Technology, 50(1), 129–140. https://doi.org/10.1177/1477153517722053

Munsell, A. H. (1916). A Color Notation. Princeton: Geo. H. Ellis Company.

Newton, I. (1704). Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light. London: Sa.Smith and Benj.Walford.

Ostwald, W. (1926). Die Farbenfibel. Leipzig,: Unesma.

Snellen, H. A. (1995). Willem Einthoven (1860-1927): father of electrocardiography – life and work, ancestors and contemporaries. Dordrecht: Kluwer Academic Publishers.

Thompson, P., May, K., & Stone, R. (1993). Chromostereopsis: a multicomponent depth effect? Displays, 14(4), 227–234. https://doi.org/10.1016/0141-9382(93)90093-K

Endnotes


[i]      Some clarification is deserved here: by phenomenological, I mean in the psychological sense of subjective experience or that which presents as an apparent phenomenon. This as opposed to ontological, relating to the nature of being and the ‘actual’. Both are nuanced terms, but here I attempt to make a distinction between that which appears to be real through experience (the former) and that which appears to be independently, objectively real (the latter).

[ii]     The Commission is abbreviated from the French as la Commission Internationale de l’Eclairage (CIE).

[iii]    The so-called tri-stimulus model is loosely based on our understanding of the light-sensitive ‘rods and cones’ of the human eye, colloquially described as red, green and blue, but more precisely as having areas of spectral sensitivity in short (“S”, 420 nm – 440 nm), middle (“M”, 530 nm – 540 nm), and long (“L”, 560 nm – 580 nm) wavelengths.

[iv]     Adobe’s colour framework as used in their ‘Creative Cloud’ applications is largely based on the Munsell system although Lightroom (the photographic management tool) borrows from more recent ideas about psychophysical colours.

[v]      In optical (biological) science, this is considered the result of differing wavelengths of light being displaced in non-corresponding retinal positions of each eye during binocular viewing. This as opposed to the type of distortion well known to photographers as ‘purple fringing’ where lenses produce inconsistent focus points across the chromatic spectrum resulting in a distracting coloured halo, particularly when objects appear silhouetted against a bright background.

[vi]     Einthoven invented the first practical electrocardiogram (ECG) in 1903, receiving the Nobel Prize in Medicine in 1924.

[vii]    A teapot in this case – something that would be recognisable regardless of its colour.

[viii]   The renaissance artists of the 15th century are usually given credit for introducing perspective to fine art although they weren’t the first to do so really. The Italian masters Giotto and Duccio, nearly a century earlier, had begun to explore depth and volume as an early form of perspective – but it was the Florentine architect and designer, Fillipo Brunelleschi, working in the early 1400s who is generally recognised as the pioneer of true ‘linear’ perspective

I’ve been an instructor for Adobe software, among other applications, since the late 1990s and continue to teach and lecture in design and creative software. So, it’s about time I finished what I’ve written in parts for any number of courses over many years.

At the time of writing, it’s easy to assume that graphic design is pretty-much synonymous with Adobe software – what is now branded as the ‘Creative Cloud’ applications of Photoshop, Illustrator, InDesign and Acrobat not to mention their tools for motion graphics and video editing, Premiere Pro and After Effects; their web design apps, Dreamweaver and Muse; the dominant photographer’s application, Lightroom and many niche products such as Dimension, Animate (nee, Flash) and Character Animator; and finally, the growing list of mobile apps such as Spark, Capture, Sketch and Draw.

It’s a long and exhaustive list and over the years Adobe have worked hard to maintain their dominance in the creative space. They were pioneers in the development of fundamental technologies such as the Portable Document Format (PDF) and the printer language, PostScript, which was the underlying technology of the venerable Apple Laserwriter, the first affordable laser printer in the 1980s. 

Adobe were also among the first to make web code accessible to designers, initially with their PageMill program, followed by GoLive, and finally Dreamweaver which they acquired in the 1990s. They also continue to dominate video editing and compositing despite competition from Apple’s Final Cut Pro.

But with the increasing move towards server-side ‘cloud’ applications and a growing number of independent developers producing effective alternatives, Adobe no longer have the field entirely to themselves. Besides this, so much of our engagement with information now happens on the web and through mobile devices that the conventions of graphic design as a primarily print-based craft, developed with desktop software are changing.

This book, then, is not just a guide to using Adobe software. Of course, Photoshop, InDesign etc form a crucial part of the discussion but the focus is on principles and concepts that are more fundamental than the use of software. Indeed, there are so many ‘tutorials’ on Adobe software available on YouTube alone that it’s hard to imagine the value of yet another source. 

Craig Kirkwood.