Aerial perspective: Theory & warnings

Today, I have been editing the entry for aerial perspective in the Glossary for my books. As I was making my corrections, I had the idea that readers of the Posts Page of this website might like a preview of this and future Glossary edits that I feel might interest them. So, to start the ball rolling, here is a slightly expanded version of the one on aerial perspective, with four images added.

Aerial perspective: Between any viewer and the surfaces of the objects at which they are looking lies a portion of the earth’s atmosphere. In addition to the transparent gases that make up air, this contains quantities of dust and other particulate matter (such as the water droplets in mist and, more evidently nowadays, various kinds of pollution). The effect of the intervening atmosphere on the appearance of distant hills and objects seen is well known to us all. We all perceive distant parts of landscapes being bluer and/or greyer  and lighter than nearer parts, and objects seen through mist or fog appear progressively greyer and lighter as the distance between them and us increases. Many artists dating back to the Italian Renaissance, most famously Leonardo da Vinci (1452 – 1519) and Claude Lorrain (1600 – 1682), have demonstrated the value of applying these principles in paintings. So convincing was their effect, that they were adopted as “rules”  by the French  Académie Royale de Peinture et de Sculpture soon after it was founded in the mid seventeenth century.  No one would dispute that the images in Figure 1 and Figure 2 produce a sense of progressive distance.


Aerial perspective
Figure 1 : Leonardo da Vinci – detail of “the Virgin of the Rocks”


Aerial perspective
Figure 2 : Claude of Lorrain- Classical landscape



  • Although the theory explaining aerial perspective is scientifically sound and although it virtually always has an important effect on how we perceive both distant parts of landscapes and objects on misty days, it has no discernible effect on how we perceive objects within an arms length. So at what distance does its influence become apparent? The answer is that it varies according to the composition and density of the particles floating about within it.  Thus, on dry, bright days of the kind that often follow abundant heavy rain, when the air has been washed clean, the visibility of atmospheric intervention is minimised, whereas on a hot sultry or misty days, when the air is at its fullest of dust and pollution, it is maximised. In practice, this can mean that on a clear day its effect on the appearance of objects hundreds of meters away may not be discernible.
  • Despite these facts of appearances, over the years, I have found that many students, when they first come to my Painting School, have been in the habit of adding blue to objects much nearer than that (in one exceptional case, a newcomer, when painting a bunch of flowers in a vase, added blue to the colour of flowers and foliage at the back of the arrangement, arguing that it made it look further away). When I see this being done, it tells me is that the student in question cannot have been looking at the near/far colour/lightness relativities. If so, how can they appreciate the amazing riches of colour relations in nature? They need to learn that rules are not for following blindly, but for testing, a process which will always open doors of awareness.
  • To further complicate the situation, there are a number of other variables that can result in people perceiving more distant surfaces of a particular colour as brighter and more fully saturated than nearer surfaces of the same colour: In other words, the opposite of the aerial perspective rule. For example, in summertime, the green canopies of distant oak trees that are illuminated by bright sunlight will look lighter and brighter than those of nearer oak trees should they happen to be situated in the shadow of clouds. Also, a boat on a lake that is painted with a fully saturated red that is actually further away from the viewer than a boat painted with a desaturated red will still look further away. If we made a painting of them, matching as best as possible the colours as we see them, the laws of aerial perspective would predict that the further boats would be perceived as being nearer than the nearer boat. Clearly there needs to be a way of depicting distance that has nothing to do with the representation of atmospheric intervention. Luckily there are several of these, including overlap, relative size and texture cues, but only one of them necessitates the use of colour. Unfortunately, this colour-dependent way of enhancing illusory pictorial space appears to be little known, despite its solid foundations in well known history, its sound scientific underpinning and the ease of its practical application. Much of my book “Painting with Light and Colour” is devoted to giving it new life. If you want to know more, read chapters already published on this website and watch for later Posts.

Two examples of minimal effect of aerial perspective, containing contradictions to the laws as exemplified by Clause Lorrain.

John Constable (1776 – 1837) was a great admirer of Claude Lorrain, but he looked more carefully at nature. Figure 3 and Figure 4 are images of two of his paintings that contain elements that are not consistent with a rigorous interpretation of the laws of aerial perspective. See how many you can find?


aerial perspective
Figure 3 : John Constable, – “Flatford Mill”.


aerial perspective
Figure 4 : John Constable “Wivenhoe Park”.


Now look at paintings by the Impressionists – Monet, Renoir Pissaro, Cezanne, Gauguin, Bonnard, etc. – to see how much they make use of the rules of aerial perspective. Where they do make use of them, was this the result of applying the rules or of looking carefully at nature? According to what is written above, far distant hills should always actually look bluer or greyer, but what about landscapes representing the kind of distances depicted by Constable or shorter ones?

Effect of patchy cloud cover on relative brightnessess

Finally to ram the point home, here are three photographs that illustrate how patchy cloud cover can produce contradictions to the laws of aerial perspective.


aerial perspective
Figure 5 : Duller nearer/brighter further


Figure 5  illustrates an exception to the law. Due to their being brightly illuminated by sunlight, the walls of the distant church tower are much brighter than those of the house in the foreground, which is in the shadow of passing clouds.


aerial perspective
Figure 6 : Brighter nearer/duller further


In Figure 6 the situation is reversed. The walls of the house in the foreground are now brightly illuminated by direct sunlight and are much brighter than those of the church tower, which is now in the shadow of passing clouds.

Figure 7 shows:

  • The far house,
  • The strip of green field in front of it,
  • The sunlit patches of brown earth in the ploughed field,

as being brighter than,

  • The near house,
  • The ribbon of green field in the bottom left of the image,
  • The area of brown earth immediately above it.


aerial perspective
Figure 7 : Duller nearer/brighter further


In all three images atmospheric intervention is playing a part, but in Figure 5 and Figure 7, its effects are being obscured in the ways described.



Preparation for the drawing lesson

The need for preparation

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.




Diagrams and explanations from the Glossary

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.

Figure 1



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  of whole-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


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:

  • The “somosensory cortex” (an essential part of the “feel system”).
  • 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


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.


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Clarifications: what does colour mean?


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:

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.


Figure 1: The two ways light interacts with surfaces, giving information about surface-reflection profile and body colour


  • “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 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”.

Figure 2: A diagrammatic representation of the colour sphere


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 the fact that they are indeed so was already a widely accepted implication of the discovery well over 150 years earlier that colours are made in the head.

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.


Colourists : different meanings

Colourists in 20th century art

A colourist can be defined as artists who give priority to the creation of colour-based experiences in their paintings. The problem is that it can be used in significantly different ways. In two Posts, I suggest two approaches to the unraveling  the consequent ambiguities. This post contrasts the very different meanings of the word for three particular 20th century painters who have been described as colourists. The Second Post analyses its meaning when used in the phrase “Venetian Colourists”. See also The Glossary entry for “colour

First approach: Two distinct types of colourist compared

I had two artist teachers who described themselves as colourists. One was interested in whole-field colour relations and the other in local colour-contrast effects. Both represented widely accepted meanings of the word.

  • Marian Bohusz-Szyszko, the Polish artist, teacher and mathematician, thought in terms of a multiplicity of colours (in principle many hundreds of thousands) and, more precisely, the effect of each and every colour on the picture surface on each and every other colour on it.


Marian Bohusz-Szyszko – Detail from “the seven Archangels 1963–1979


  • Michael Kidner, the English “Systems Painter”, thought in terms of a very limited number of colours (for example, two, three or four) and was principally interested either in local interactions between them or in their denotative function in his systems.
                                        Michael Kidner – Primary Colours 1967


A well known American artist had different ideas:

  • Ellsworth Kelly felt that both of the approaches to colour just described divert attention from the experience of colour as itself. He came to the conclusion that the only way of providing a pure experience of colour was to cover the entire surface of a painting with a single colour.
                                       Ellsworth Kelly- Red Curves 1996


But these are only three examples and many other possibilities exist. For instance, I have met artists and viewers who seem to think that producing more or less any array of what they consider to be colourful colours qualifies them as colourists, no matter how garish and discordant the results appear to the eyes of others.

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Venetian Colourists

Defining “Venetian Colourists”

In a previous Post, I compared three 20th Century artists who have been described as “colourists”, and who had very different ideas on the place of colour in painting. I also suggested that these were only three among many possibilities.

In this second Post, I comment on the meaning art historians’ give the word “colourist” when writing about two different groups of pioneer artists,  one that flourished in the  the Italian Renaissance and the other that overturned all sorts of preconceptions in the last part of the nineteenth century.  The two groups are:

  • The Venetian Colourists (Giovanni Bellini, Giorgione, Titian, Tintoretto, etc.) and other, later artists, who kept within the same tradition (Vermeer, Turner, etc.).
  • The Modernist Painter Colourists of the late nineteenth century (Cézanne, Gauguin, etc) and early twentieth century (Matisse, Bonnard, etc.).

Continue reading “Venetian Colourists”

Contents Lists for three of my books

The subjects covered are:

1.  Drawing    2. Painting    3. Creativity

These are followed by Posts on other subjects

Preface to all three books


Chapters from “Drawing on Both Sides of the Brain”.

Other Posts on Drawing:


Chapters from “Painting with Light and Colour”:

Other Posts on colour and light in painting:


Chapters from “Fresh  insights into Creativity”

Extracts from Chapter 10: “Having fun with creativity”



Your comments on the Contents List page.

I look forward to your comments in the section provided at the bottom of each Post. When you have made them, please leave your email address and tick the box “Notify me of new posts by email.”


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Horace Lecoq Boisbaudran & Alphonse Legros

by Rodin pupil of Horace Lecoq Boisbaudran
A fast Drawing by Auguste Rodin, a pupil of Horace Lecoq Boisbaudran


Drawing by Degas, friend of Alphonse Legros pupil of Horace Lecoq Boisbaudran
Drawing by Edgar Degas, a close friend of Alphonse Legros,  pupil of Horace Lecoq Boisbaudran


This post on Horace Lecoq Boisbaudran was promised in to the New Year Letter to Students posted in the category “Painting School News“. In this I mentioned the similarities between the teaching methods of Horace Lecoq Boisbaudran and mine. In later posts I will be saying more about these. 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”