Saturday, 24 December 2016

The Science of Colour: from Newton to Turner via Goethe


A ‘Turner evening sun’ photographed from the steps of the Turner Contemporary gallery and its reflection in their café’s window. It’s of no direct relevance, but this is a relatively long post and a relaxing first image may help the reader ...

In earlier posts I have reflected on aspects of my series of modest contributions to the work of the Learning Team at the wonderful, and for me wonderfully local, Turner Contemporary gallery (e.g. here and here). It’s also rather nice that I get a credit in a couple of short films that have come out of our contact (here and here) – and even one of my many tweets is quoted in another of their celebratory videos (here – see if you can spot it, it’s near the beginning). My own appreciation of art and of those who work within and for its promotion has been transformed by my contact with the gallery and its team. However, I think this is the first time I’ve devoted an entire post to a project of theirs in which I was able to make a contribution. It’s associated with their current exhibition of some of JMW Turner’s wonderful paintings and drawings, Adventures in Colour, and it gets an entire post by virtue of the fascinating background I unearthed whilst reading up for my role.

Our protagonists. (Centre: the Turner Contemporary’s exhibition leaflet; left: Johann Wolfgang von Goethe above Sir Isaac Newton; right Joseph Mallord William Turner.  Goethe’s and Turner’s images are adapted from those at www.tate.org.uk, Newton’s from http://www.biography.com/people/isaac-newton-9422656#synopsis)
Having been trained in Isaac Newton’s theories of colour as a physics student – prisms, ‘rainbow spectra’ etc. – I found myself more and more fascinated by the influence that Johann Wolfgang von Goethe’s rather different approach to colour had on Turner’s work. Goethe came a century after Newton, and was a contemporary of Turner – although Goethe’s seminal work on colour was only translated into English, and thus made more easily accessible, in 1840. Goethe’s careful observations, made over a 40-year period, led him to reject Newton’s theory that all the colours we see are an admixture of two or more of the seven ‘rainbow’ colours he observed coming from a prism when illuminated by ‘white light’. ‘Darkness’, in this theory was simply the absence of light. By contrast, Goethe became fascinated by the boundary between light and dark, and was sure that colours emerged from the interplay between the two: in other words, ‘dark’ became an important and active component to the emergence of colour. He was, moreover, fascinated by the emotional connotations of colour: yellows and reds were warm, positive colours and blues and purples were cold and negative. Furthermore, he identified the concept of each colour having a complementary colour – look out of a window towards the sun and then close your eyes: the yellow of the sun becomes a blue ‘afterglow’; yellow and blue are complementary colours. Indeed, the concept of complementary colours becomes obvious when looking at the shadow created by an object placed in the beam of a single-colour light source. As an example, shine a green light onto the object and one will perceive a magenta shadow – the shadow is simply grey when looked at close up, but if viewed against the green surroundings our brains perceive it as magenta. This led him to define and draw a colour wheel showing the relationship between these complements. There’s so much more to all this, but I don’t want to overburden anyone with the details. To sum it all up one might say that we can explain all the optical phenomena we observe on a day-today basis using Newton’s physical theory, which has been tested out in umpteen ways over the years – even those ostensibly contrary observations of Goethe. Having said that, even though Goethe’s approach is not truly a scientific framework, his careful observations led him to some important conclusions associated with the role our brains play in our perception of colour. In that respect his ideas are actually quite contemporary. More to the point in the context of the project at the heart of this post, his observations caught the artistic imagination of Joseph Turner.

Goethe’s colour wheel showing the complementary colours on opposite sides of the circle (Image from https://en.wikipedia.org/wiki/Theory_of_Colours)
Turner was an experimenter: trying out new pigments, developing (and teaching) ideas of perspective and exploring different ways of applying colour for example. He was working at a time when subject disciplines were not as rigidly defined as they can seem to be nowadays; scientists, engineers and artists would interact quite naturally, whereas it can take a special effort to cross the imagined boundaries we have more recently defined for ourselves. The Royal Society and the Royal Academy of Arts, now wholly distinct entities, were at the time housed in the same building; Turner knew and was friends with famous scientists like Michael Faraday and Humphrey Davy, mathematicians like Mary Sommerville and engineers like Isambard Kingdom Brunel. Goethe’s ideas evidently also excited him. There is clear visual evidence of this in so many of Turner’s paintings, more especially those created later in his life. The considered use of colour to express emotion, the subtle use of light and dark interfaces and the associated use of complementary colours are all strong indicators of Goethe’s influence. Given that Goethe’s observations are focussed on human perception and emotion it’s perhaps no surprise that Turner’s later paintings, which at the time were seen by some as evidence of a deranged mind, still evoke such a powerful response from contemporary viewers. Although it would be possible to list a great many examples of paintings which demonstrate Goethe’s influence on Turner’s artistic practice, it will perhaps suffice to reproduce (below) a pair that he explicitly associated with Goethe’s ideas.

Left: Shade and Darkness - the Evening of the Deluge and 
Right: Light and Colour (Goethe’s Theory) - the Morning after the Deluge - Moses Writing the Book of Genesis. (Images from http://www.tate.org.uk) 
Both were exhibited 1843, and reflecting not only Goethe’s ideas on colour but the fascination of the time in ‘apocalyptic sublime nature’. On the left we see Turner’s play on light and dark and on the use of the more ‘negative’ colours; by contrast, on the right we have the warm positive colours being used as well as more than a passing reference to Goethe’s colour wheel.

The issue that faced me on the day of the Teachers Tea Party was how to try and encapsulate some of these concepts and theories into a 20-30 minute chat prior to going into the gallery itself. I have no idea whether what I attempted truly worked or not, since that depends very much on whether the participants are able to use the suggestions and ideas offered given the reality of their primary school classrooms. However, I’ll try to outline here a few of the things I tried out on the day by using some ‘home-made’ images.

In terms of Newton’s theory of colour, life is relatively easy in that most people have seen a spectrum – from water droplets as they generate a rainbow and probably also from a prism. The image top left provides a good example of the generation of a spectrum by splitting white light into its colours. This splitting occurs via a process called refraction: when light enters a medium, in this case the prism, the speed of light varies depending on its wavelength (i.e. its colour) and this causes the light to be ‘bent’ to different degrees. My simplified demonstration used a couple of laser pointers, one red and one green; I attached them to a ruler in order to help ensure they were pointing in the same direction. They enter the prism at the same angle, but emerge at different angles. Although I only possess an inexpensive perspex prism, the demonstration worked tolerably well and a clear separation between the red and green spots on a distant wall was easy to see.

A good starting place for Goethe’s ideas was the projection of a slide showing a simple grid of black squares on a white background: grey ‘blobs’ may be perceived the corners of the squares. This is an easy way to signal the start of Goethe’s exploration of the interfaces between light and dark since we see something emerging in our vision which, were we to zoom in on the space, disappears: we need the light/dark interface and the imposition of our brains to make it work.
The next attempted demonstration was less successful at the venue due to the ambient lighting – it worked well at home with the curtains closed, so a re-run under more controlled lighting conditions would almost certainly improve things. (It probably goes without saying that colour-blindness, which affects about 4½% of the population – primarily men – will affect the results.) In order to illustrate our perception of complementary colours I projected a PowerPoint slide of uniform green and then created a shadow by holding an object in the light’s path: even with the background lighting it was still just about possible to see a slight magenta tinge to the otherwise grey shadow. A similar trial using a projected red slide led most people to say they could see a green tinge to the shadow. Now, the shadow is in fact grey; it’s not coloured at all in reality, but our brains have imposed on it the complementary colour to that of the light source. This can be demonstrated by getting close to the projected slide and focusing solely onto the shadow, which is simply grey (- maybe use a cardboard tube to help shut out the surrounding colour?). To see this effect in a more controlled setup, take a look at this video, about three minutes in. Next time you look at Turner’s paintings (and the work of a great many others since his time) pay attention to the colour of his shadows, and particularly those depicted with the sun low in the sky and thus giving a red/yellow light.

Returning now to our prism, it’s possible to use it to replicate something more of what led Goethe to state that colour emerges from the juxtaposition of light and dark. Instead of adopting the ‘Newtonian’ setup and using the prism to cast it rainbow spectrum from sunlight, try instead to look through the prism towards the window and look carefully at what happens in the vicinity of its stiles/rails or grills. There’s a need to experiment a little with the orientation of the prism, but eventually coloured bands will emerge at the edges – and the order in which the colours appear will differ depending on whether one is looking to the left or right, or above or below, the light/dark boundaries between glass and frame. This made no sense to Goethe in the context of Newton’s theory: not only had he seen colours not part of Newton’s basic seven-colour spectrum when exploring shadows (e.g. magenta from green illumination as above) but now even the spectra he observed through a prism differed from Newton’s.

My own simplistic attempt to illustrate these effects is shown above (- an elaborate setup involving an up-turned bin on top of my desk). Notice the appearance of the red end of the classic rainbow colours to the right or above a light/dark interface and the blue end to the left or below. Is this proof that Newtonian theories ought to be thrown out and replaced? No. I made the point above that all the colours we see, and which Goethe so carefully observed as he was getting to grips with our perception of complementary colours, may be generated by the admixture of two or more of Newton’s basic spectrum of colours. The apparently more complex observations associated with looking through a prism at light/dark interfaces may equally be explained using Newton’s theories. It this latter case, each part of the window glass is refracting the sunlight and therefore dispersing its various colours – but all of these ‘rainbows’ overlap and we see only the average of them all, which is of course white light/sunlight. The exception to this is at the edges of each window pane since at those places there can be no such averaging process. For instance, immediately to the right of the frame the refracted light through the glass overlaps with nothing to its left and we end up seeing the red half of the rainbow colours. It’s a little like having the window frame sit in the middle of the spectrum I’ve shown in the image shown third up from here.

Finally, one of my personal favourite paintings – or, rather, my talented wife’s version of it – serves to illustrate the way in which Turner made explicit use of the emotional connotations of colours described by Goethe. In his Rain, Steam, and Speed - The Great Western Railway (1844) he uses colour to convey the sense of power and excitement he felt in the context of the newly-emerging steam railways. Such paintings are not ‘accurate representations’ of a thing, place or process so much as evocations of their impact on the artist – and perhaps thereafter on some of us who have viewed their work down through the years.

For those wanting to learn more about Goethe’s observations and ideas I recommend the four-part video which begins here.

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Postscript for any readers in the Northwest USA: Since posting this, I have been made aware of an up-coming exhibition of paintings which includes work by JMW Turner alongside other wonderful paintings. For details, please see here. Also, there is an interesting associated profile of JMW Turner on the Artsy site here.



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