My two previous the Posts provided links to Chapter 12, “Local colour interactions” and Chapter 13, “Colour constancy”, from my book “What Scientists can Learn from Artists”. ThisPost provides a link to Chapter 15, “The other constancies”. Below the two images you will find an edited version of the “Introduction” to this chapter. As with other Posts, if you find that the subject matter interest you, you can click on the link below to the .PDF version of the chapter as a whole. The images illustrate two of the visual perceptual problems with which artists have had to come to terms.
Introductory to Chapter 15
Colour constancy is by no means the only constancy of visual perception. There are many other constancies and all are fundamental to the ability of the eye-brain to make practical use of visually acquired information. Paradoxically, although their name suggests stability, they are responsible for the veritable “shifting sands of appearance” which, in its various guises, constitutes one of the main problems for artists seeking to obtain accuracy in drawings or paintings from observation. This is because they ensure that, when we look separately at any two similar features of appearances whether they be whole objects, parts of objects, sections of contour or colours, there is a very strong tendency to see them as being more similar to one another than objective measurement would dictate – often a great deal more so. Our visual systems upset the measured parameters of external relationship by relentlessly forcing them towards normative dimensions and values. As a result, the constancies involve enlarging and diminishing, squashing and stretching, revolving, darkening and lightening and modifying colour. Any list of the constancies of particular interest to the artist should certainly include (a) size constancy, (b) shape constancy, (c) orientation constancy (d) lightness constancy and (e) colour constancy.
It was unequivocal evidence of “induced colour” and “colour constancy” that triggered the realisation among scientists towards the end of the Eighteenth Century that colour is not a property of surfaces in the external world but phenomenon that is made in the head. Once this idea had been digested, it gained momentum and evidence began to pour in to suggest that all visual experience is a creation of the eye/brain combination. This game-changing paradigm shift was to lead, not only to the birth of the science of “visual perception”, but also to fundamental changes in the practice of artists, either when drawing or painting from observation or when seeking control of pictorial dynamics. This is why the “constancies” and “simultaneous contrast dynamics” play such an important role in my books on the practice of painting and drawing. It is also an important part of the reason why I have written “What Scientists can Learn from Artists”, the last volume of my four volume series that explains the science behind so many of the ideas elaborated upon in the remaining three volumes. In going more deeply into the subjects that play such an important role in these books about artistic practices, it plunges us deep into the astonishing nature of the working principles of visual perception. Apart from the sheer wonder this must surely generate, knowing about the ways these determine how we “look” and how we “see” should have a significant benefits for artists: The deeper understanding and appreciation of the extraordinary things that are happening in our heads should help artists to:
Deal with the many practical problems that invariably face them when drawing or painting from observation
Make more creative use of their physical and conceptual tools.
The next Posts I will be chapters from the science volume.
A life changing event
This Post on “colour constancy” is the first from “What Scientists can Learn from Artists”. Its inspiration derives fromEdwin Land’s irrefutable demonstration of the phenomenon of “colour constancy”, which proved to be a milestone in the search for an understanding of a subject that turned out to be of key importance to the understanding of how we “perceive surface”, “sense space” and are “aware of of lighting conditions”, all subjects of key importance to the ideas presented in “Painting with Light and Colour”.
A photo of the equipment used by Land for his epoch making colour constancy demonstration.
A reprise of the “Introduction” to the chapter and a link to a .PDF version of it (no need to read it twice: if you read it below, you can skip it in the chapter)
Links to Posts from “Painting with Light and Colour”, all of which (particularly chapters 7 to 11) have a debt to research that grew out of the colour constancy demonstration.
As explained earlier, a key event in my life was the encounter with Professor Marian Bohusz-Szyszko. The ideas he shared set me off on a lifelong journey of discovery. My first step was to set about testing his seemingly extravagant assertion that it is only necessary to follow two rules to guarantee a good painting:
There must be no repetition of colour on the same picture surface.
All the colours used must be mixtures containing at least a trace of complementary.
After four years of experimenting, I proved, at least to my own satisfaction, that there is a special quality in all paintings that abide by these two rules. It is difficult to describe, but it involves the creation of a sense of pictorial space and harmony.
Fortunately, a troubling paradox arose that would eventually have a profound effect on the development of the ideas presented in this book. It concerned the Professor’s physics-based proof of the invariable variability of colours in nature. This asserted that no two parts of any surface will reflect exactly the same wavelength combinations into our eyes due to:
The complexity produced by the inter-reflecting surfaces
Variations in viewing angles and distances
The paradox is that, if the light reflecting from two parts of a surface can never be characterised by the same wavlength combination, how could artists repeat colours on a picture surface? Even if two regions were painted with exactly the same pigment-colour, how could these appear as the same?
Other people might already have known how to resolve this mystery, but for many years I had no idea how to do so. My first inkling of a solution came after many years, as a result of reading a paper by Edwin Land, the inventor of the Polaroid camera. In it was a powerful demonstration of the phenomenon of “colour constancy” and an attempt to explaining it. What the demonstration showed was a region of colour within a multicoloured display (henceforth referred to as the MCD) being perceived as remaining the same, even when the experimenter changed the combination of wavelengths being reflected from it. I was excited because here were two colours being perceived as the same despite reflecting different wavelength combinations into they eyes? For me it was a eureka moment. However a big problem emerged for it was soon clear to me that the explanation of the colour constancy demonstration suggested by Land was not neurophysiologically plausible. An alternative had to be found. I could never have guessed at the treasure trove of discoveries that would come out of my struggles to provide it. This chapter describes Land’s demonstrations in the context of an earlier attempt at explaining colour constancy. The next chapter introduces our neurophysiologically plausible colour constancy algorithm.
Members of the University of Stirling Vision Group
In many places in my books, I acknowledge the importance of the role of colleagues from University of Stirling in the development of the new science-based ideas put forward in them. In particular I mention cooperations with scientists from various departments who later were to join me in the University of Stirling Vision Group. The most important of these were:
Alistair Watson (Physics, psychology and computer imagery).
Lindsay Wilson* (at the time working on aspects of visual perception).
Also, although Peter Brophy* did not join our group, he was an ever-available and important source of information on the biochemistry of the brain.
The founding of the Vision Group.
It was in the Autumn of 1984 that Alistair, Leslie and I took the first steps in the setting up of the University of Stirling Vision Group, which was to have many meetings attended by the above named colleagues and other members of the various interested Departments. Its starting point was a package of ideas developed by Alistair and myself, and two core algorithms based on them, produced by Alistair. These were:
A “colour constancy algorithm“, capable of modelling both spatial and temporal colour constancy, which was inspired by our interpretation of how this phenomenon is achieved by human eye/brain systems. As a preliminary step to achieving this main objective, the algorithm has to pick off the information about surface-reflection. Since it was obvious that the reflected-light contained information, we speculated upon how it might be used by the eye/brain. Due to my interest in picture perception, we focused on its potential for computing surface-form, in front/behind relations, and the wavelength composition of ambient illumination.**
A “classification/recognition algorithm”, based on our interpretation of how human eye/brain systems achieves their primary task of enabling recognition.***
We could not help being excited by the early tests of these algorithms and the speculations concerning their potential. In our enthusiasm to push matters further, Alistair suggested we should seek the help of other researchers, particularly ones with expertise in:
Mathematics and computing.
Visual perception with special reference of visual memory.
It was at this juncture that, having decided on a name for what we were hoping would become a collaborative group, we contacted Leslie Smith for his mathematical and computing skills. But this was only a start. Once Leslie was on board, we approached Bill Phillips, whose long standing interest in visual memory had led him to take the plunge into the recently emerging domain of neural networks and learning algorithms. After many Vision Group meetings, much sharing of ideas, many hours spent working on implementations of algorithms, and the writing of a number of working papers, we decided to submit a suite of five grant applications to the Science and Engineering Research Council, who had let it be known that they were looking for groups of researchers working on the use of computers to model the functional principles of neural system. The stated aim of the SERC was to set up a small number of “Centres of Excellence” in this domain. Not only were two of our grant applications accepted (one submitted by Bill Phillips and one submitted by Leslie Smith), but also our university was encouraged to create a brand new Centre for Cognitive and Computational Neuroscience . This empire absorbed the University of Stirling Vision Group which ceased to have an independent existence. Its coming into existence also coincided with my departure from Stirling on my way to founding my Painting School of Montmiral, where I intended to put theory into practice both in my own work and in my teaching. I also had hopes of confirming and, with any luck, extending the theory. Also after leaving Stirling University, Alistair and I were founder members of a small software development company which used ideas developed within the Vision Group as a basis for creating an image manipulation tool. ****
* The links to Bill, Leslie, Lindsay and Peter relate to their current status. Alistair, Karel and Ranald all retired or died before the Internet became the essential information source it has since become.
** My book is full of examples of how fruitful this speculation proved to be.
When new students at The Painting School of Montmiral are first faced with a live model in a figure drawing class, the majority of them give little time for preparation, even for long poses. Within a matter of seconds, even experienced artists have embarked upon active mark-making. It does not seem to occur to them that, before drawing the first line, it might be useful to spend time familiarizing themselves with the situation that faces them. If this is the case, they will almost certainly be denying themselves an important opportunity.
The feeling-based drawing lesson
At the heart of my book, “Drawing on Both Sides of the Brain“, is a feeling-based drawing lesson that is described in three chapters. Chapter 9(link below) is about getting ready for drawing the first line. Chapter 10 (to follow) gives a blow by blow account of the main lesson in which:
Precise instructions are given concerning the preparation and execution of every line and every relationship.
Detailed reasons are offered for each and every one of these instructions. These relate to scientific studies of how artists coordinate their visual-analytic and line-output skills when drawing from observation.
Chapter 11 (to follow) suggests follow up exercises.
Preparation in previous chapters
All the chapters preceding Chapter 9 have been preparing for this lesson. Thus, they have discussed:
The pros and cons of widely used teaching methods.
The importance of scientific findings in the development of artists ideas.
How more recent scientific findings relating to the eye/brain’s analytic-looking and motor-control systems can help with issues of accuracy, line production speed, self-confidence and self expression.
Preparation in Chapter 9
Chapter 9 is likewise getting things ready for the drawing lesson, but in a much more specific sense, starting with practical issues such as setting up the easel/drawing board, establishing a viewpoint, deciding whether to shut an eye, etc. But it also introduces a certain amount of science-based information that will be useful in explaining reasons for the instructions used in the drawing lesson.
As Chapter 9 contains footnotes that refer to diagrams with explanations to be found in the Glossary, I have included three of these:
Figure 1 is the flow diagram representing the main factors that contribute to the analytic-looking cycle.
Figure 2 indicates regions of the neocortex (new brain) involved.
Figure 3 provides a mapping of eye movements showing glides and saccades.
The boxes and arrows in Figure 1 can be related to regions in the neocortex illustrated in Figure 2. Notice that Visual Area 1, which takes input from the retina via the optic nerve, supplies information not only for the preconscious processes that enable recognition, but also for the subsequent consciousness-related ones that accompany analytic-looking (This is why it is labelled “twice used information resource”).
In addition, the diagram indicates the key role of memory stores (whether short-term or long-term) in enabling both recognition and learnt-actions. It also calls attention to the importance of context and feeling in building them up and ofwhole-life experience in determining how they do so. But perhaps the most important lesson that can be drawn from it is that recognition takes place before analysis. Thus it can be asserted that, in an important sense, “we know what we are looking at before we are consciously aware of it”.
Recognition also takes place before the implementation of learnt-actions, such as those that guide artists when drawing contours or making any other kind of mark. Accordingly, we can draw “what we know” about an object-type on the basis of the multi-modal, preconsciously acquired information made available by the very limited number of looks that are required to enable recognition (seldom more than one or two). In other words, the eye/brain acts as if further analysis of the object itself is unnecessary. The diagram also indicates the role of non visual-inputs in enabling recognition. For example, we may recognise something, in whole or in part, by its sound, smell or feel and can in princple complete the process of doing so without confirming what it is visually.
Figure 2 maps a number of the functional divisions in the neocortex (new brain). These can be related to the stages of the analytic-looking cycle as diagrammed in Figure 1. Thus:
The arrow labelled “visual cortex” points to the location of “visual area 1” in Figure 1
The region from there down to “temporal lobe” corresponds to the labels “preconscious multimodal processing” and “recognition” in Figure 1.
The motor cortex mediates “learnt actions” in Figure 1.
The parietal lobe underpins “conscious analytic-looking” and “the constancies of shape, size, and orientation” in Figure 1.
However, the area in Figure 1 labelled “context” and “feeling-based memory reflecting whole life experience” is more difficult to place, but would include:
Parts of the “frontal lobe” with its links to the emotional centres in the old brain. These are thought to be involved in the choice between “good” and “bad” actions and the determination of “similarities” and “differences” between things or events, both of which are essential to developing the skills that underpin drawing from observation (as explained in Chapters 9 – 11).
The frontal lobe, along with old brain regions including the hippocampus, is also thought to play an important part in the creation and retention of long-term memory.
Figure 3 is based on a photographic record of typical eye movements in which slow moving glides (wobbly blue lines) are interspersed with faster moving saccades (straight red lines with arrows to represent speed). The glides provide a constant stream of same/different information, while the saccades enable an intermittent averaging of input that is useful for neural computations that require knowledge of ambient illumination. The average glide/saccades combination lasts approximately one third of a second.
Other Posts that publish chapters from “Drawing on Both Sides of the Brain”
This Post discusses the relationship between fast drawing, learning and personal expression. It is an important subject because there seems to be a connection in many people’s minds between speed and expression. Various questions arise. The most basic one is whether there is any necessary connection at all.
In all my books I assume that personal expression can come in a multitude of ways: fast, slow, passionate, quietly sensitive, and all gradations between these extremes. This Post concentrates on the use of fast drawing. The main arguments are found in Chapter 8 of my book,“Drawing on Both sides of the Brain”.
The questions raised in Chapter 8 provide a means of taking a critical look at the widespread practice of starting life drawing sessions with poses that are so short that they force fast drawing. Those who advocate this practice, believe that their shortness will increase the likelihood of creativity and personal expression. In Chapter 8, I question this belief.
Chapter 8 and subsequent chapters between them explain how to use accuracy as a means of enhancing information pickup speed and, thereby, to learn to draw faster, with more authority and in ways that foster personal expression.
NB. In the chapter, reference is made both to illustrations found in a later chapter of the book, and to texts in another book in the series. As neither of these is as yet available to the reader, I have added them below.
Texts and illustrations referred to in Chapter 8
Four drawings of pollarded trees on the esplanade, Castelnau de Montmiral. They were made in 3 hrs, 30 minutes, 10 minutes and from memory respectively. They are extracted from Chapter 11 of “Drawing on Both sides of the Brain”.
A computer controlled experiment: an extract from Chapter 8 of“What Scientists can Learn from Artists”:
This extract comprises a summary of ideas coming from the main experiments and how they led to the computer controlled experiment which showed that preparatory looking helped rapidity of information pick-up:
“These ideas were amongst those that we had in mind when we came to consider the results from the main experiments. In particular they influenced our thought when we reflected upon the revelations of the video-tape record. One result was a hypothesis that needed testing. The argument that gave rise to this depended a variety of factors. If both comparison and the organisation of actions disrupt aspects of visual-memory, then copying must require a longer-term memory-store to guide a coordinated and efficient looking strategy. The superior performance of the skilled adults for drawing familiar objects from memory indicated that this function could be performed by long term memory. However, what about unfamiliar objects or the complex curves which describe the ever changing shapes of familiar ones? As suggested above, efficient visual analysis of these might require the creation of a purpose-specific memory store, structured with the help of longer looks, such as those recorded on the videotape. Thus, our hypothesis was that the function of the longer looks is to create a memory store containing knowledge of what to look for later. The advantage would be reaped in terms of the pick-up efficiency of the inter-saccadic glances. Given that time taken for each of these is fixed, it follows that the learning process enables more information to be picked up in the same time. Such a feat could only be achieved if appropriate, purpose specific memory structures had been created.
The computer-controlled experiment in question was used to test these ideas. A sequence of different two-line RSL models was displayed on a computer screen. At a given time after a model appeared, one of the two lines disappeared and the subjects were asked to copy the one that remained. The time before the disappearance was either one-third of a second or five seconds. When the subjects had completed drawing the visible line, they pressed a button which caused the second line to reappear for either one-third of a second (allowing time for one glance) or two-thirds of a second (allowing time for two glances). The question was whether the information collected in the five-second preliminary look would lead to better pick-up of information by the final glance or glances. The answer was a clear ‘yes’. Without the preliminary five-second look, the subjects were all-over-the-place when doing their best to copy the second line, whereas with it, they performed almost as well as if the image was there in front of their eyes.
This result gave strong support to the hypothesis that temporary knowledge, acquired as a result of appropriately organised looking behaviour, could play a vital role in achieving copying accuracy.”
Chapters from “Drawing on Both Sides of the Brain”.
I have met many people who think that copying photographs is somehow cheating. Certainly it can be used as an easy way of sidestepping the challenges (and opportunities) provided by copying directly from nature. But this does not mean that it can never be justified.
The main purpose of this Post is to publish Chapter 7of my book “Drawing on Both Sides of the Brain”, which discusses the advantages and disadvantages of copying small, static, two-dimensional photographic images, as compared with confronting the full force of nature, in all its dimensions. Its conclusion is that both possibilities have their place. Rather than condemning the practice of copying photographs out of hand, artists might be well advised to work out what is the best option in the circumstances of the moment.
The chapter also considers an earlier and, for many years, much used memory-based alternative to copying photographic images.
CLAM is an acronym for “continuously looking at the model“. It describes a teaching method, suggested by Kimon Nicolaїdes and popularised by Betty Edwards. However, these authors describe it as “contour drawing”.
Since 1941, when Nicolaїdes‘ book “The Natural Way to Draw” was published posthumously and started its life as the most influential book on drawing published in the twentieth century, his method has proved its value as a powerful teaching tool. However, in addition to its well established advantages, the way Nicolaїdes‘ and Edwards taught it has significant disadvantages. Chapter 6 in my book “Drawing on Both Sides of the Brain” explains both the strengths and the limitations of the method.
Why avoid talking of “negative spaces ” or “negative shapes”?
The title of Chapter 6 of my book “Drawing on Both Sides of the Brain” is “Negative Shapes”. Some people may be surprised to find that I question the widespread use by art teachers of the phrase “negative shapes” and of its equivalent, “negative spaces“. After explaining the reasons for the popularity of its use as a means of bypassing the problems due to familiarity, I argue that it has significant shortcomings. In the light of these, I suggest that there are alternatives which avoid its disadvantages without relinquishing any of its advantages. Perhaps more importantly, these provides better ways of using drawing from observation as a tool for discovering the unique characteristics of objects in the world around us.
The chapter featured in this Post is about the paradigm shift in artists thought that took place in the latter part of the nineteenth century, and some of its consequences in terms of the Modernist teaching methods that were to emerge in the twentieth century.
The chapter featured in this Post tells how, over the centuries, artists changed the way they conceived the function of the sketch. From being a step in the Academic method, by which predetermined elements were organised into a composition, it was used in more open-ended essentially Modernist ways. The chapter also explains what I mean by drawing with the “feel-system” and, in doing so, prepares readers for the crucial role it plays in later chapters. For this reason it is key to the ideas developed in my book.