How head movement can help accuracy in drawings from observation
All the books correctly say that, when using the perspective frame and other traditional devices for obtaining accuracy in drawings from observation, head movement must be avoided at all costs. Teachers also warn students, who are trying to obtain accuracy when drawing from observation, that any movements of the head can substantially change both internal and external relationships in the scene they are depicting. Although what they say is true, their warning glosses over the fact that such movements can be a powerful tool for homing in on accuracy. The purpose of this Post is to provide the link below to “Chapter 17 – Head movement“, which explains why. Below that link I have included a slightly edited version of the Introductory to that chapter.
Having learnt to find the eye-line, we are ready to make further use of theanalogy of the opening window. The purpose of the next two chapters is to become better acquainted with some of the many anomalies of visual perceptionthat regularly plague attempts at accurate drawing from observation. In this waywe will learn to become more sensitive to aspects of appearances that we might otherwise overlook. Three particularly pervasive sources of anomalies are:
Turning the head (whether from side to side or up and down)
The imposition of axes of symmetry by our visual systems.
The constancies of size and shape.
This chapter and the one that follows give examples of each of these, which willappear under three headings: “head movement”, “axes of symmetry” and “theconstancies”. Although for explanatory purposes, it is convenient to treat them separately, we find that any combination of the three can be affecting our perception at the same time. We start with this chapter on “head movement”
Images illustrating head movement
The three images below show three different views of long boundary the wall of the esplanade. They provide a bit of realism to line drawings found in Figures 1a, 1b, 1c & 1d in the Chapter 17, to which this Post is inked.
Long wall to the right
Long wall to the left
Long wall head on
Chapters so far published from
Book 1 and Book 2 of “Drawing on Both Sides of the Brain” (Volume 1 of the series of four volumes)
I have to thank two short women and a tall man for revealing to me that “axes of near-symmetry” are intimately related to the phenomenon of “orientation constancy”. The tall man was looking over a low wall and he was depicting its top as sloping down from left to right. The short women drew it as horizontal. The fact that the man could see a particular field beyond it that the women were unable to see, meant that he was the only one of the three that was being influenced by what I later came to call the “bakery facade illusion”. The women were right that the top of the wall was horizontal. To find why the man was also right, click on the link below to Chapter 18 of my book “Drawing with Knowledge”. Its title is “Axes of symmetry, recession and the constancies”.
Establishing an eye-line is the first step if you are going to use the the rules of linear perspective for constructing an image. The same is true, if you are using the same rules as an aid to drawing from observation. However, whereas its use in construction is straightforward, its use in drawing from observation is far from it. The purpose of this Post is to explain why. Below you will find a link to “Chapter 16 – Finding the eye-line“. I have also included a slightly edited version of the Introductory to that chapter.
After the session in the studio, we move out into the street. From the demonstrations using the opening window, we have learnt that any straight edge that lines up with the eye-line remains horizontal no matter at which angle it is relative to our line of vision. If we are to make use of this knowledge, we need to find the eye-line. As a general rule, students who come to my school assume that this is easy to do, but the evidence of the drawing they make suggests that they are likely to be deceiving themselves.
Making it easy to see the slope of the esplanade wall
Asking for trouble: explanation why in the chapter
Chapters so far published from
Book 1 and Book 2 of “Drawing on Both Sides of the Brain” (Volume 1 of the series of four volumes)
The eye is full of surprises. The biggest ones come from the structure of retina that is situated at the back of it. The purpose of this Post is to provide a link to images and explanatory captions that tell us more about this starting gate of visual processing. At first sight, much of what we find strikes us as bizarre. But, when we delve more deeply, we discover the considerable advantages of the way things actually are. It turns out that nothing would work nearly as well as it does, if things were arranged any differently. The images and their captions will go a long way towards explaining why. In the process, they will help readers to get a better understanding of how the eye/brain combination makes practical use of the information contained in the ever-changing patterns of light coming into the eye.
The link to the diagrams
Click on the link below to access the images and captions referred to. They are extracted from ‘The Glossary‘ to the four volumes I am in the process of publishing on this website.
Upon leaving the retina, the neural signals travel in two directions. Some go up the optic nerve to the region of the neocortex known as ‘Visual Area 1′. Others take a completely different route that makes contact with the regions of the “Old Brain”. These play a central role in visual perception as we experience it. For example, they play their part in eye movements, spatial awareness, affective responses, multimodal processing, whole-field relations and much besides. Images and captions relating to both these routes will be posted later on this website, in a separate entry, entitled, “Visual Regions in the Brain”.
Images of blood vessels, neurons and and neural processes in the eye.
The human retina contains a very large number of neurons (cells) and a very much lager number of neural of processes providing links between them. It also features a dense network of blood vessels that supply blood to them. Together these make a significant barrier to the passage of any light that strikes them. Until I learnt better, this light-blocking function did not seem to be of much of interest.
What changed my mind was the discovery that the light-sensitive cone and rod receptors, that transform light-energy into neural signals, do not face towards the incoming light, but away from it. Consequently, the light coming into the eyes has to penetrate this light-impeding layer of neurons, neural processes and blood vessels, before it reaches the receptors. To add to my surprise, it turned out that the light-receiving end of the receptors is buried in a layer of dark matter. It was some time before I realised how these seemingly bizarre arrangements make possible visual perception as we know it.
The barrier confronting the light that enters the eye
It turns out that the barrier of neurons, neural processes and blood vessels compensates for the fact that the rod receptors are very much more sensitive to light than the cone receptors. The benefit of this state of affairs is that it enables a necessary degree of functional equality between the responses to the incoming light of the two different receptor-types. Needless to say, there would be no the equalling up, if the light striking the less sensitive cone receptors were to be subjected to the same impediments. This explains why the forces of evolution have created a gap in the neuron and blood vessel barrier in front of the region known as the fovea, exactly where the incoming light strikes the cone receptors.
Glare-blindness
If the equalling up process did not take place, the rod receptors would be bleached out whenever the incoming light was strong enough to activate the cone receptors. The result would be a massive degree of glare-blindness in daylight conditions.
Dire consequences
If they were effectively blind, the rod receptors would not be able to participate in daylight visual processing. One consequences would be that no neural computations of whole-field relations could take place. One of the many aspects of visual processing that would rendered impossible would be the separation of reflect-light from body-colour. As a result there would be neither colour constancy, nor the use of the information residing in the separated out reflected-light. If this were so, pretty well all that I have written in my book “Painting with Light” would be nonsense.
Burying the receptors in dark matter
The burying of the light-sensitive receptor heads in the dark matter is easier to explain. It prevents the light from scattering from one receptor to the next and, consequently, reduces blurring.
Figure 1: Blood vessels blocking light from the ‘rod’ photosensitive receptors. The small darker disc is where the light sensitive ‘cone’ receptors are located. Notice that no blood vessels impede the passage of incoming light to these.
Figure 2: This image of a small section of a network of neural processes gives an inkling of an idea of the extent to which these these can block the incoming light. For reasons explained above, the blockage only applies to ‘rod’ photosensitive receptors. It does not apply to the ‘cone’ photosensitive receptors .
Figure 3: A diagram of cell-types in each of the five layers of the retina. The massive numbers of each of these contribute to the blocking of the light arriving at the ‘rod’ photosensitive receptors.
Some numbers and sizes
Although the precise number of neurons and neural processes in the retina is unknown, it is certainly in the hundreds of millions. One estimate for the sum total of light sensitive receptor cells is approximately 150 million. All this packs into an astonishingly thin layer (less than 0.5 mm). The extent of retina is not much larger than a 10p piece.
A reference
If you want a comprehensive account of the component parts and structure of the retina, you could consult the relevant pages of the website of the The National Library of Medicine. You will find them dizzyingly more complex than the grossly oversimplified information given either above or in the ‘Glossary‘ extract.
The purpose of this “Post” is to provide the link (below) to my introduction to “Chapter 14 : Linear Perspective“, the second chapter of “Drawing with Knowledge” (the second BOOK in the two book volume). The main subject dealt with is uses and abuses of Linear Perspective. The chapter explains the purpose for which the rules the rule of linear perspective were developed and how over the years artists and teachers came to use them for other purposes for which they are not suited. It also explains how the rules of linear perspective can be used in new ways. A preliminary idea of what this means can be found in first paragraph of the “Introductory” to this chapter, which I have included below. Also see below for links to all published chapters from “Drawing with Feeling“, the first BOOK in the two book volume.
“Introductory” – from Chapter 14 : Linear perspective
Academic tradition divides the subject of “perspective” into two aspects, known as “aerial” and “linear”. Aerial perspective concerns colour changes due to the influence on appearances of atmospheric particles situated between the eye and an object being viewed at a distance, and is dealt with in a separate volume. In this book attention will be confined to linear perspective. Moreover, to avoid misunderstandings, it is important to stress that no attempt will be made to compete with the many existing texts on this subject which demonstrate that, when properly applied, the well-known laws can enable the construction of moderately realistic images without the need to actually look at anything. As far as I know there is nothing of interest to add to these, although, a great deal needs modifying in many of the texts on the subject which regrettably give us oversimplified and therefore misleading versions of this complex and elegant subject. Rather, in this volume, the laws of linear perspective are treated in a completely novel way: not as a set of instructions for the placement of lines on but as a tool for guiding looking strategies. This transformation is achieved by placing them in the context of ideas coming both from 19th century research into visual phenomena and from much more recent discoveries relating to the functioning of eyes and brains. In PART 2, the subject of anatomy will be treated in an analogous way for analogous reasons.
Some images relating to the theme of linear perspective
Illustrating Brunellesci’s perspective mirror set-up (maItaly : Italian History and Art)
Pietro Perugino, Christ handing the keys to St Peter 1481-1482.
School of Athens by Raphael in the Stanza della Segnatura 1509-1511
Albrecht Dürer – perspective device for obtaining accuracy
A list of chapters from “Drawing with Feeling“, book 1 of “Drawing on Both Sides of the Brain“
The purpose of this ‘Post’ is to provide the link (see below) to my introduction to “Drawing with Knowledge”, the second BOOK in the two book volume (See below for links with the published chapters of “Drawing with Feeling“, the first BOOK in the two book volume). The two main subjects dealt with are Linear Perspective and Anatomy.
Do the rules of perspective and anatomy help or hinder accuracy?
A key property of the world we live in is that we will never perceive any of its contents as the same on more than one occasion. The list of reasons why includes the influence on appearances of:
The almost infinite variety of species and object types
The invariable uniqueness of genetic differences between members of the same species
Ageing
Environmental conditions, including variations in the direction and strength of primary and secondary light sources, degree of atmospheric filtering, etc.,
Occlusions by other objects
Viewing angles and viewing distances
Visual illusions.
However seeing something (even the same object) as the same on more than one occasion is what we have to do if we are to recognise it. This means that:
Recognition and the content of our long term memories must depend on generalisations
There will always be a degree of uniqueness in the appearance of every object we try to draw or paint from observation.
From all this we can conclude that:
Achieving accuracy in drawing or painting from observation will always require finding out about aspects of appearance that cannot be stored in our memories.
Following the rules of linear perspective or anatomy can never achieve accuracy in drawing or painting from observation.
So what can they help us to do?
The rules of linear perspective and of anatomy can help us construct plausible images from the imagination (See examples below)
The rules of linear perspective and of anatomy can help us to know what to look for.
The second of these provides the main subject matter of this book.
Some studies using linear perspective and anatomy.
Linear Perspective
Structural study of complex objectPiero della Francesca : studies of a headPiero della Francesca : Use of linear perspective in his painting “The flaggelation of Christ”
Anatomy
Visalius : anatomical study from his famous book Leonardo da Vince : study of arm musculatureMichelangelo : Page of studies
A list of chapters from “Drawing with Feeling”, book 1 of “Drawing on Both Sides of the Brain”“
This Post introduces Chapter 22 from my book “Painting with Light and colour”. It uses one of my paintings to discuss many issues that relate to viewing conditions. These all apply to all paintings, but it is difficult to find information about them in other books. Indeed, it was not until I began work on paintings including numbers of thin lines that I became fully aware of many of them. My awakening was a result of the coming together of many strands of the story I have been telling in my series of four books.
The dogmas of Marian Bohusz-Szyszko (see Chapter 1),
My interest in the debates relating to “illusory pictorial space” (see Chapters 7-10 in “Painting with Light”, the first part of this volume),
My interest in the Modernist Painters obsession with what they described the “integrity of the picture surface”* and its dynamic implications in the history of “Modernism in Painting“**
In general, whenever images of paintings are transferred to the computer screen, many of their qualities are lost. Sometimes this can be an advantage, but never for paintings that follow the dogmas of Professor Bohusz-Szyszko. This is particularly true for the images using thin lines discussed in this chapter and the next. Often, you will just have to take it on trust that the effects discussed are as described.
An image of a painting with twelve of orange thin lines
* If you ask Google “What is a Modernist painter”, you get the following excellet summary: “Modern art includes artistic work produced during the period extending roughly from the 1860s to the 1970s, and denotes the styles and philosophies of the art produced during that era. The term is usually associated with art in which the traditions of the past have been thrown aside in a spirit of experimentation.” However, if you had asked Manet, Cézanne, Van Gogh, Matisse, etc., etc., whether traditions of the past had been thrown aside, you would find that it was by no means all of them.
** Google says that the “integrity of the picture plane” is a phrase coined by the influential art critic Clement Greenberg in his essay “Modernist Painting”. It concerns the issue as to whether the fact of creating an“illusory pictorial space” interferes with perceptions of the “objectness”of the actual picture surface. This was a question of primary importance to the “Early Modernists” from the late 1860s onwards. For them, as explained in Chapter 6 of my book “Fresh Perspectives on Creativity”, the fact of the possibility of being aware of the actual surface of paintings was one of the reasons for what they believed to be their inherent superiority relative to photographs. Their belief was that, since“deception is immoral”, painters must avoid it at all costs. Despite the difficult-to-comprehend this questionable argument, it stuck for about a century. Thus, in the 1960s, it was still a potent aspect of the teaching of my two mentors, Professor Bohusz Szyszko and Michael Kidner. The difference between the “Early Modernists” and Clement Greenberg was that the former (and Professor Bohusz-Szyszko) thought it possible to depict illusory pictorial space without destroying the integrity of the picture surface. In contrast, Clement Greenberg asserted the impossiblilit of any such thing, as didPiet Mondrian and a number of earlier painters, plus a whole list of later artists, including Michael Kidner and Ellsworth Kelly.
As those who have read “Painting with Light”, the first Book in this Two Book Volume will realise, the early Modernists and Professor Bohusz-Szyszko got it wrong. The use of unmixed repeated colours do not disrupt the picture-surface, but rather the illusory pictorial space. They do so because our eye/brains read them as being on the picture surface and, consequently, as jumping out of any illusory pictorial space, which is allways behind it. It is thus, the integrity of illusory pictorial space that is disrupted.
Earlier chapters from “Painting with Light and Colour”:
This Post provides a link to the introduction to BOOK 2 of “Painting with Light and Colour“. It deals with what I have described as “body colour” and is subivided into four PARTS:
Part 1: Colour and feeling (Chapter 19).
Part 2: Local colour interactions (Chapters 20-24)
Part 3: Shadows, shading and highlights (Chapters 25 -28)
Part 4: Concluding syntheses based on both “Painting with Colour” and “Painting with Light”( Chapters 29-31)
Ealier, in Chapters 8, 9, and 10, much was written explaining about how “optical mixing” was central to Seurat’s ideas about “painting with light”. Here it is used to introduce lesser or unknown aspects of the subject of interactions between adjacent regions of colour (the subject of this and the next four chapters). The more familiar aspects have been given less space because they have already been treated authoritatively in books by Joannes Itten * and Joseph Albers** of the Bauhaus,*** as well as in countless other books and magazine articles, with varying degrees of reliability.
Like Chapter 20, these earlier chapters also take “optical mixing” as their starting point. However, their concern is not with contrast effects but with other topics:
This Post introduces Chapter 21 of my book “Painting with Lightand Colour”. It focuses on a subject that is dealt within every book, every article and in every classroom in which the subject of colour dynamics is treated. It was first described by Michel Eugène Chevreul in 1839. The name he gave to it was “simultaneous colour contrast“.
Its potential for use in paintings was popularised by Eugene Delacroix. It was picked from him by the Impressionists and many of their Modernist Painter successors. In the twentieth century when so many artists turned to non-figurative productions, it came to be treated as a subject in itself. A particularly influential part in this process was played by teachers at the Bauhaus. Of special importance were Johannes Itten and Joseph Albers, both of whom produced books exploring the possibilities of colour contrast effects . Both had a widespread and lasting influence on artists and art education. The purpose of this chapter is to introduce their ideas as a preparation for going beyond them. Doing so will provide the subject matter for this chapter as well as chapters 22, 23 and 24.
