When I arrived at art school in the late 1960s, ambiguity was one of the first things we were expected to think about. Over the years I have learnt what an important role it has played in artist’s thinking over the last on hundred and fifty years.

Definition

Ambiguity occurs whenever two or more interpretations are in competition with one another. They may be within any domain of sensory experience or across domains, but here it is considered in relation to the visual domain.  The purpose of this Post is to present some of the reasons why ambiguity should be of fundamental interest to artists, particularly if they are:

• Wish to depict illusory pictorial space.
• Seeking to create either harmony or discord in their paintings.

An illustration of ambiguity

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A good example of a high level of ambiguity is provided by the well known vase/face illusion illustrated in Figure 1, in which we can see either a vase or two silhouetted faces. However, it is important to notice that, although we can choose between the vase or the two faces interpretations, we cannot stop the ambiguity of the situation providing a degree of tension. The force of this can be sensed by comparing the right hand side face with the identical face in Figure 2 in which there is no left hand side face to create the vase shape. Clearly, by removing the ambiguity between the vase and the two faces interpretations, the face is easier to look at. The question for artists is whether they want to maximise ease of looking or to create works with some degree of tension.

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Escaping ambiguity

As explained below, it can be argued that all paintings exhibit an ambiguity between their pictorial contents and their presence as objects with real surfaces. The the only way the escape this is to make use of one or more of the strategies that are available to us for that purpose. Not counting that of looking away altogether, these depend on concentrating attention on details at the expense of wider context, which can be done either by focusing down or by moving closer. However, although both these manoeuvres work well enough for reducing ambiguity in everyday visual perception, our eye/brains can seldom completely exclude the influence of alternative interpretations in paintings..

Real picture surface versus illusory pictorial space

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One type of ambiguity has had a pivotal place in the history of painting. It is that between perceptions of an illusory pictorial space and awareness of the real picture surface. Historically speaking, it became important when the Impressionists and other early Modernist Painters were looking for ways in which their hand-painted images could combat the threat posed by the high levels of realism produced by the newly available photographic method. They feared that the fact that it was so easily and quickly obtained in photographs, would undermine their livelihood.

Luckily for them and for the history of painting, they saw photographic images as deceiving the eye and hit on the now seemingly absurd idea that this deception was morally reprehensible (an idea that was still influencing artists in the 1960s and beyond).  Abruptly, for progressive painters at least, the trompe-l’oeil, which for so long had been the goal of artists, became something to be avoided at all costs.

The solution found by these Modernist painters was to introduce ambiguity. Their idea was to provide a counterpoint to perceptions of illusory pictorial space by emphasizing the reality of the picture surface. The painting, by Berth Morisot, illustrated in Figure 3, provides a good example of how brush marks and surface texture can be used as a means of preventing the trap of deception. What these pioneer artists reasoned was that the impossibility of being able to enter the illusory pictorial space created by the realism of the image without being aware of these indicators of real paint and real surface, meant that a salutary ambiguity would be inevitable.  What they could not have guessed is that the wealth of unexplored possibilities that the picture surface/illusory pictorial space dichotomy would make available, not only to them but also to their successors during well over a century.

An example of competing cues

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The Modernist Painters were also interested in another kind of ambiguity in which attention is drawn in competing directions. For example, Figure 4 shows Pierre Bonnard going a long way towards obscuring the features in his wife’s face, presumably with a view to allowing the telling gesture of the hand to take on more significance than it would have done had the eyes, nose and mouth been more clearly delineated. However, since this strategy completely fails to override the eye/brain’s built in tendency to give faces more importance than hands, the result is a pull in both directions. The consequent dynamic equilibrium is of central importance to the experience of looking at the drawing. Just as in Figure 1, it is difficult to look at the vase interpretation without being influenced by the two-face interpretation, it is difficult to look at either the hand or the face to the complete exclusion of the other.

Figurative versus abstract

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Another area of competition is between pictorial dynamics based on figurative content and ones that involve non-figurative relationships such as those between colours, contours, textures, etc.. The more the Modernist Painters found their interest turning to the latter, the more they sought ways of playing down the influence of the former. A first step in this direction was that of reducing the strength of the cues that make recognition too easy (as in the case of the face in both the drawing of Marthe by Pierre Bonnard, illustrated in Figure 4, and the portrait of Ambrose Vollard by Pablo Picasso, illustrated in Figure 5). A second step was to get rid of figuration and its attention-distracting pull altogether.

Seeking to eradicate ambiguity

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Many artists saw great potential in the removal of figuration but did not want to get rid of illusory pictorial space, which they felt gave extra dynamic possibilities to interactions of colour, contour, texture, in front/behind relations, etc. Others were still troubled by the immorality of deceiving the eye and sought to eliminate illusion altogether. They wanted all regions of their paintings  to be perceived as being flat on the picture surface, as no doubt was the intention of Michael Kidner when making the work illustrated in Figure 6.

However, these purists were soon to realise that achieving this objective might prove more difficult than they had imagined. It seemed that no matter how hard they struggled, if a picture surface, had more than one region of colour on it, their eye/brains would find ways of creating perceptions of illusory pictorial space within it. In other words, they seemed unable to prevent some of the regions of colour appearing to be either in front of or behind others. Even the simplest two colour painting, such as the one by Ellsworth Kelly illustrated in Figure 7, would not do, for it gives at least some people the impression of a landmass, a horizon and a sky.

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Sculpture?

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In the end, the only solution seemed to be one colour paintings, of which many appeared in the 1950s and 1960s. These included the series of blue paintings, embarked upon by Yves Kline in 1957, and several works by Ellsworth Kelly on the lines of Figure 8. The only ambiguity remaining lay in the question whether these were correctly classified as “paintings”. Some might think it more appropriate to describe them as “sculptures” or, merely, as “objects hanging on a wall”. For those artists who identified (in my view falsely) the search to remove the ambiguity as being of the essence of “Modernism in Painting“, it was time for “Post Modernism“.

Harmony and discord

To find out what this has to do with “harmony and discord” please consult previously posted chapters from “Painting with Light and Colour” and excerpts from the “Glossary”. In particular I suggest reading:

Relevant chapter

• Basic factors in painting

Relevant excerpts from the Glossary

• What are colourists? (1): Some of the many meanings of the word
• What are colourists? (2): Difference between meaning of the word for Venetian Colourists and for Modernist Colourists?
• What does the word “colour” mean?

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Clarifications

Experience with new students suggest that there is a need for clarifications on the meanings of the word “colour” and a number of related words and phrases. The following excerpt from the Glossary to my books on drawing and painting provide answers to the questions listed below, and many others.

• What is meant by “body colour”?
• What is the difference between “brightness “ and “lightness”?
• What is meant by  “reflected light”?
• How can colour be used to enhance perceptions of illusory pictorial space?
• Are “black” and “white” colours?
• Are cast shadows “black“?

What follows relates to several already published Posts. For example:

• What are colourists? (1): Some of the many meanings of the word
• What are colourists? (2): Difference between meaning of the word for Venetian Colourists and for Modernist Colourists?
• “Painting with Light and Colour”, Chapter 8 : Seurat and Painting with Light
• “Painting with Light and Colour”, Chapter 9 : Seeing Light
• “Painting with Light and Colour”, Chapter 10 : Illusory pictorial space and light

Colour 1: Colour and surface

In everyday language the word “colour” has four main meanings. The first three of these can be explained in terms of the interaction between surfaces and the light that strikes them as diagrammed in Figure 1.

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• “Surface-reflection” : A part of the incident light is reflected directly back from the surface without changing its wavelength combinations.  This is“surface-reflection” and is one of several sources of information that enables the eye/brain to create the experiences of surface-solidity, surface-form and in front/behind relationships.
• “Body-colour”: The remainder of the incident light enters surfaces and interacts with the pigments in them, such that some of its wavelengths are absorbed (i.e; turned in to non-visible electromagnetic energy) and the remainder is scattered about within the surface, before being scattered back out again into the eyes of the viewer. It is this scattered-back-out light that gives surfaces their “body-colour”, enabling us to see the surfaces as their characteristic colour (e.g. red, blue, brown, grey, skin colour, leaf colour, earth colour, sky colour, etc.).
• “Transmitted light”: In some cases, a surface can be viewed from the side opposite to the light source,  in which case, it is  said to be “translucent”.  When this is the case, the light that enters a surface and interacts with the pigments in it is scattered out on the other side, into they eyes of a viewer. Accordingly it is described as “transmitted light”. It is this that that gives us the colours of stain-glass windows and translucent leaves when seen against sunlight.  In the virtual absence of surface-indicating reflected-light, we perceive such colours as both surfaceless and formless. Two other examples of familiar, perceptually surfaceless colours are the blue of the sky and the colours of the rainbow.

The fourth meaning is more prosaic:

• Paint or pigment colour: The word “colour” is also used to describe any selection from the gamut of paints, pastels or crayons used by artists to give colour to their paintings. Thus we talk about the “colours” contained in our paint box, or of the “lemon yellow” and “cobalt blue” tubes of paint to be found in it.

Colour 2: Colour, light and physics

While in everyday language “colours” are referred to with words like “red”, “blue”, “yellow”, “pink”, “brown”, “grey”, etc., and we are all familiar with what they mean, physicists have preferred to describe them in terms of electromagnetic energy and combinations wavelengths and levels of intensity. Accordingly, they are likely to describe the three cone-receptor types in the retina at the back of the eyes as being relatively sensitive to “short”, “medium” and “long” wavelengths. However, even physicists can lapse into referring to them, more colloquially, as “blue”, “green” and “red”,  a slippage which can lead to significant misunderstanding. If we wish to understand the nature of colour vision, it is important to realise that  knowing the wavelength of the light coming into the eyes from a surface is by no means the same as knowing its colour. Light has no colour: Colour is a creation of eye/brain systems gathering and comparing information from arrays of inputs (as explained  elsewhere in these Posts, as well as in the chapters of my books).

One consequence of this fundamental truth is that, although there is indeed a correspondence between wavelength profiles and the colour perceptions that they stimulate, this is not as simple as many people seem to believe. It is only occurs if all the wavelength profiles entering the eyes from all parts of the scene being analysed during the colour-creating process are taken into account. Likewise, our experience of colour in paintings does not depend simply on the absorption/reflection properties of individual regions of pigment colour but rather on the absorption/reflection properties of all the regions of pigment colour on the entire picture surface. In other words, they depend on  “whole-field-colour-relations”.

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Colour 3:

As with all words with a long history, the word “colour” has evolved in terms of its meanings and it is therefore it is important to be careful when using it. Most commonly it is used to describe visual sensations that are experienced as attributes of surfaces or regions of surfaces in the external word. We talk of “red” roses or “green” grass because we have learnt to use these words to describe our experience of “red” and “green” objects that we come across in daily life. However, in the eighteenth century, scientists of visual perception realised that colour is not anything of the kind. Rather it is a creation of eye/brain systems based not only on information coming into the eyes from the surface that is being perceived as coloured, but also from the surfaces that surround it. In short, they realised that the experience of colour is both brain-made and context-sensitive. Together these two insights made it clear that the colour of a surface cannot be equated with wavelength combinations of the light reflecting from it, as physicists had been doing. For more on this see the section on colour constancy under the constancies in this Glossary.

Soon after the physicists made new contributions to the progress of understanding about colour by going deeper into the subject of the information that the eye/brain picks up from surfaces. What they found was that it is made up of two components with very different properties. In this series of books these are called “body-colour” and “surface-reflection”. Figure 1 shows that when daylight, containing all the visible wavelengths strikes a surface it is divided into two parts:

• One part penetrates the surface. When inside, some of its wavelengths are absorbed and others, having been scattered around inside, are scattered back out again into the eye of an observer. This is the “body colour” (what we see as the green of leaves, the yellow of ripe corn, the flesh colour of flesh, etc.). As far as I know, nobody has estimated the number of different body colours in the visible world, but there are clearly at least many thousands.
• Another part never enters the surface. Rather it is reflected directly off it according to the rule the angle of incidence is equal to the angle of reflection. Since no light is absorbed during this process, the incident light and the reflected-light contain the same wavelength combination. In the diagram both are shown as being the same “white” light.

In the interests of simplifying its message, Figure 1 only shows one ray of incident light. In the real world light arrives at surfaces from a combination of primary light sources (coming from one or more different directions) and a multiplicity of secondary light sources of different of intensities (coming from a multiplicity of different directions). While primary light sources can have fairly predicable wavelength/intensity profiles, secondary light sources never do: The likelihood of any two combinations of them being the same is negligible. The resulting complexity is such that no part of any one surface reflects the same wavelength/intensity combination as any other part of it.  Likewise, no two surfaces in any scene reflects the same wavelength/intensity combination. Physicists would describe the consequent variety of in the composition of the reflected-light that results as  “infinite”. However, for the perceptual scientist, the limitations on the sensitivity of their visual systems restrict the number of nuances of which human eyes can be aware. How many is disputed, but it is generally agreed to be in the millions.

Colour 4 : black and white are colours

In the 1980s Semir Zeki, when investigating area V4 of the visual cortex, found twenty-two “colour coded cells”. These respond to body-colour independently of their wavelength profiles. The twenty-two not only included “violet”, a colour that has no simple wavelength equivalent, but also “black” and “white”. This means that the eye/brain responds to achromatic regions of surfaces in precisely the same way as it responds to regions of blue, green yellow, orange and red. This definitively resolved the question as to whether black and white are colours.

Although Zeki’s dicoveries provided incontrovertical proof that colour is made in the head, this conclusionhad been reached and generally accepted by scientists of visual perception well over 150 years earlier when they were trying to make sense of the phenemenon of colour-constancy.

Colour 5: Shadows

More recently, the discoveries of the physicists have been combined with the ideas of the perceptual scientists to explain how the eye/brain is able to separate surface-reflection from body-colour. Details of how this is done are given in “What Scientists can Learn from Artists”, Chapters 13 and 14. However one part of the computation depends on the sudden changes in the profile of the reflected-light that regularly occur at the edges of regions of colour (whether at edges of regions of different pigmentation within the same surface or at edges of the surfaces themselves) being equated with changes in body-colour. However it turns out that the computations concerned cannot distinguish sudden changes in actual body-colour from those that occur at the edges of cast shadows (due to sudden changes in intensity relative to adjacent illuminated regions of surface). Accordingly our eye-brain systems classify these erroneously as “body-colour”.  Accordingly, as far as the eye/brain is concerned  the colour of shadow is just as much a colour in its own right as the blue of the sky, the red of a tomato, the yellow of a lemon, the green of a leaf, the white of snow or the black of soot.

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Horace Lecoq Boisbaudran came to my notice in 2014. In later posts I will be saying more about him. In brief, I was amazed and gratified to find that the research upon which he based his teaching has more in common with my research than anything else I have come across. Although the exercises he proposed differed in many details from the ones that I suggest in my books, we have in common the idea that training the memory requires rigorous exploration of the unvarying uniqueness in the appearance of every object. Horace Lecoq de Boisbaudran’s pupil Alphonse Legros, who actively promoted his teacher’s ideas, became a close friend of Edgar Degas. It may therefore be no coincidence that it was he who provided the best synthesis of Horace Lecoq Boisbaudran’s philosophy that I know:

“It is all very well to copy what you see; it is much better to draw what you only see in memory. There is a transformation during which the imagination works in conjunction with the memory. You only put down what made an impression on you, that is to say the essential. Then your memory and your invention are freed from the dominating influence of nature. That is why pictures made by a man with a trained memory, who knows thoroughly both the masters and his own craft, are almost always remarkable works; for instance Delacroix.

Where my teaching is substantially different from that of Horace Lecoq Boisbaudran is the emphasis I put on training the “feel system“.

Meanwhile here is an extract from the “Glossary”  to “Drawing on Both Sides of the Brain” that provides an introduction to his ideas and his influence. I have also added the entry for Alphonse Legros, described as his star pupil, who had great success in spreading his ideas to both his own generation and the following ones.

Continue reading “Horace Lecoq Boisbaudran & Alphonse Legros”