Friday, 12 August 2016

A short introduction to colour

What is colour?


Light, without which we can’t see anything, is a form of electromagnetic radiation flowing from the sun or other source and is made of a range of wavelengths. The number of waves passing a given point each second is a wave’s frequency. Wavelength and frequency aren’t the same thing, but what matters is that we see these different wavelengths/frequencies as different colours.

The longest wavelength of light we can see is red and the shortest is violet – all wavelengths together form what we call the visible spectrum:



This range of colours is continuous, but we break it up with our familiar and somewhat arbitrary colour labels such as red, green, orange and so on.

These visible light waves are the only electromagnetic waves the human eye can see. There are many other forms of electromagnetic radiation, such as X-rays, ultra-violet and infra-red, that don’t enter into the range human vision can detect, just as there are sounds too high or too low for us to hear. We can however feel infra-red as heat, or experience the burning of our skin thanks to ultra-violet.

Rays from the sun or lamps are known as ‘white light’ but contain all the colours of the rainbow. This goes against our intuition, because white seems like an absence of colour, and when we mix up all our paints we don’t get white, we get mud. Nonetheless, white light is in fact the sum of all the wavelengths of light. This was demonstrated by Isaac Newton when he observed that a prism, via refraction, bends rays of light by different amounts, splitting up white light according to the different wavelengths within it. We see these differences as a range of colours, namely the coloured band of the spectrum. (There's a nice video about it here.)



These wavelengths don’t really have colours at all. Colours are not physical properties residing in the spectrum, any more than the sounds we hear are physical properties of vibrating air. Colour is a sensation created by our sense of vision, nervous system and brain to help us interpret the light emitted or reflected from the physical world around us. Colour isn’t an illusion, either – it’s an interpretation of real data, namely the variable wavelengths of visible light.

Of course, the way we perceive light and colours is affected by many variables, such as the position of the sun, atmospheric effects, north vs south light, and so on.

Non-spectral colour


A colour evoked by a single wavelength (or very narrow range of wavelengths) in the visible spectrum is known as spectral or monochromatic colour. Perhaps surprisingly, it is also possible to perceive colours that do not appear in the spectrum. White, black and shades of grey are colours, as are magenta, brown and olive-green, but you won’t see any of these in a rainbow, or in the spectrum thrown up by a prism.

Red, orange, yellow, green, blue, violet. No magenta.
Photo: E Gregory (Flickr).


These non-spectral colours are produced not from a single wavelength but from a combination of wavelengths. Sometimes people claim that colours like magenta ‘don’t really exist’, but they are forgetting that colour is a sensation created by our biology from light data, not a property of light. White light isn’t made of a single wavelength either, and isn't part of the spectrum. In fact, we rarely see monochromatic colour in our daily lives, because the world is a complex environment of tints and shades and reflected colours.

Another consideration is that the spectrum is composed only of hues. There are other elements of colour, namely value (how light or dark it is) and saturation (how intense it is), that introduce further variation beyond what appears in the spectrum. Thus brown may be thought of as a dark, less intense yellow or orange. In short, there is more to colour than just the visible spectrum.

Why objects have colour


Our experience of the coloured world is of light reflecting off surfaces. White light contains every colour but we don't see all objects as white. This is because objects’ physical properties absorb and reflect different wavelengths of light.

When the sun shines on a lime, for example, the reason the lime looks green is because it’s made of stuff that reflects green light more than it reflects the other colours, which get absorbed and transformed into heat.



A lemon reflects yellow light; white objects reflect all colours; black objects reflect little or no colour and instead absorb all wavelengths of light (and therefore heat). At night the level of light is too low for colour to be reflected off objects, which is why everything looks black. More accurately, of course, objects don’t normally reflect a single, pure colour but a range: the lime will mostly reflect green but will also reflect some of the neighbouring yellowish and bluish hues for example. 

Again, objects have no colour in themselves; when light shines upon them they appear to have colour to an observer. If the light itself is coloured, that affects how we see the object. In red light the lime will appear black, because the red light gets absorbed and there is no green light to reflect.

The colour of an object also depends upon the perceiver. Humans have good all-round colour vision, though a minority are colourblind. Other animals often see more or fewer colours than we do.

Hue, value and intensity


There are three aspects of colour: hue, value and intensity.

Hue


Hue is the name of a colour. When we say something is red, green, blue etc we are describing its hue. Below is a digital painting I made of an apple.



These apples are identical except for their hue: one is red, one is green. We can also name variations of each hue, such as yellow-green or blue-green.

When we talk about the colours of the visible spectrum, we are really only talking of hue, specifically the range of hues visible as monochromatic light.

Value


Value or luminosity refers to the lightness or darkness of a colour. Below, the apple on the left combines hue, value and intensity. The greyscale one on the right shows only value. It demonstrates that value can exist without hue.



Value measures the amount of light being reflected from an object. The terms tint and shade refer to lighter and darker versions of a colour. Getting the values correct is arguably the most important consideration when dealing with colour, as poor handling of light and dark is more noticeable than a hue being a bit off.

Below I’ve made a scale of value of one colour (red) plus a greyscale version:



Intensity


Intensity is also known as chroma or saturation. It is a measure of how strong or weak the colour is. Here is my apple again, but with varieties of intensity.



The leftmost apple is the most intense. The middle one is less intense but still looks realistic. The rightmost is starting to look grey. People sometimes confuse saturation with value; a saturation scale like the one below helps show the difference. All the blocks are the same value, but they decrease in saturation until the red has turned grey:


A colour in shadow cannot have the same intensity as a colour that is better lit, and bright light can wash out intensity too. For this reason the most intense colours are usually found in the mid-tones of an image, while the lights and shadows are less saturated.

Primary colours of light


If white light can be split into the visible spectrum, the reverse is also true: the coloured rays combine to make white when they are mixed together again.

Most visible colours can be made by mixing just three: red, green and blue (RGB). We call these primary colours. If we look very closely at the pixels on a TV screen or computer monitor, we see that even white is made of these three colours, and that yellow for example is made of red and green.



Trichromacy 


RGB technology flows from the way we sense light. There are three primaries because the six million colour-sensitive cells in our retinas known as cones come in three types: L, M and S, responding to long, middle and short wavelengths respectively. (There are also 120 million rods which primarily detect light and dark and are important to night vision.) Our eyes convert light energy into chemical signals and the brain creates colour sensations based upon differences in the responses between the three types of cone.

Why are there three cone types? We can’t have a separate receptor in our eye for each one of millions of individual colours. Instead our biology has settled on the more efficient solution of three receptor types sensitive to different parts of the spectrum, whose outputs are combined to create a broad range. There’s no cosmic law that says there must be three types – it’s just a solution nature came up with.

This use of three ‘channels’ to enable animals to interpret a full spectrum of colour is called trichromacy, a theory pioneered by the likes of Young, Maxwell and Helmholtz. A minority of people experience colour blindness or dichromacy, having only two receptors instead of three and therefore a more limited range of colour vision. There is even a very small number of tetrachromats who have four receptors.

While sensitive to a range of wavelengths of light, each cone type responds to a certain range more than the others. It is sometimes thought that each cone type ‘detects’ red, green and blue respectively. In reality the cones’ ranges of sensitivity overlap. Individual cone types do not detect individual colours or wavelengths – instead, a colour is created by comparing all their responses.

The illustration below shows the range of sensitivity of the three cone types superimposed upon the spectrum. L and M cones are sensitive to all wavelengths whereas the range covered by S cones is narrower. Their ranges peak at green, yellow-green, and blue-violet.


Based on an illustration by David Briggs.

R, G and B don’t exactly match up with the peak sensitivities of the cones, but they do make the best colour mixing primaries, because each stimulates one cone type more than the other two, producing the widest variety of responses and therefore colours. (It is inaccurate to say that the L, M and S cones are sensitive to R, G and B respectively, but they are commonly described as doing so even by science educators because it is near enough and has become a convention, albeit a misleading one.) Thus the three cone types effectively divide the spectrum into three bands of red-orange, yellow-green and blue-violet; thanks to convenience and tradition we label these colours more simply as red, green and blue. The three primary colours are not an innate property of light itself, but a feature of our physiological response to it.

Trichromacy can’t explain all our colour experiences, so current thinking combines this with another theory called opponency.

Opponency


Opponency was first proposed by Ewald Hering in 1892. It used to be a separate theory of colour vision to trichromacy, but today is seen as complementary to it. It does complicate things, which is perhaps why it’s often left out of explanations of colour.

There are some colour combinations we can experience, but there are others we can’t. We can experience yellow + red = orange, but not green + red = green-red. We can experience blue + red = purple, but not blue + yellow = blue-yellow. For some reason we can’t perceive red and green, or yellow and blue, simultaneously.

We also experience after-images. If we look at a colour for a while then look at a blank page we see a ghostly image of its complementary colour (we’ll explain complementaries next time). This seems to tell us something about how colour works, but trichromacy alone can’t explain why it happens.

Opponency argues that as well as trichromacy’s three channels, there are also opponent channels of three colour pairs – red-green, blue-yellow and white-black, though the latter doesn’t affect our colour sense.


Activating one colour in a pair inhibits the other colour in the pair, so you can’t see both paired colours at the same time. This is known as hue cancellation, since they cancel each other out. This is why we don’t experience red-green or blue-yellow.

With opponency, we can better understand RGB colour mixing. We can already grasp why magenta follows from the mixing of red and blue light, because it contains colour from both. The same goes for blue and green light making cyan. But it’s puzzling how red and green lights can make yellow. Remember that what we label ‘red’, ‘green’ and ‘blue’ should more precisely be ‘orange-red’, ‘yellow-green’ and ‘blue-violet’ – yellow is in fact present in the other two lights. When we know that yellow is created from red-orange and yellow-green light, the phenomenon is easier to understand: the red and green components of the lights cancel out due to opponency, leaving us seeing yellow.

This also explains why we see RGB as white light when combined. The white is not really a mixture of the three. Rather, the red/green elements and yellow/blue elements within the three RGB lights cancel out, leaving the light colourless. And the theory explains after-images: when you stare at one of the colour pairs for some time, its cells get fatigued and stop firing, allowing the opposing cells of its pair to fire unhindered.

Current thinking is that the opponency process follows trichromacy as a further stage of colour perception. This combination of trichromacy (occurring at receptor level) and opponency (occurring at neural level) forms a more complete theory known as zone theory.

The four opponent hues of red, yellow, blue and green are known as psychological primaries, another conception of Hering’s. Thanks to opponency they are the only hues that aren’t made from each other and are thus unique or ‘pure’. For example, if you look at orange you can see it as a mixture of the adjacent yellows and reds, but you can look at red without imagining it being made of anything other than red. (If we think green looks like blue + yellow this comes from our experience of mixing paints.) This makes the psychological primaries the ‘true’ primaries, lending them a certain emotional power. This may explain why they are popular among designers, as in the famous Windows logo (right).

Additive and subtractive colour


Obviously, light is a different medium to paint, so there are two kinds of primary colours: primaries for mixing light, and primaries for mixing paint.

Additive colour


With light, you start with the absence of light, i.e. black, then add colours to get to white, so it is known as additive colour mixing. The more colours you add, the more white it gets.



You can try this on your computer by adjusting RGB values in an art program’s colour picker. If R, G and B are all 0 we get black. If one of the three colours is pushed up to the top value of 255 we see it at its maximum saturation. If all three are set at middle values we see grey – dim white light, if you will. If all three are pushed up to 255 we see white. (If you try to mix red and green you get yellow, which is confusing unless you know the theory of opponency.)

You also get white when you mix just two complementary colours. An example will help this make sense. Yellow and blue light added together makes white; well, remember that yellow is created from red and green, so if you add blue light to yellow light you are mixing blue, red and green, i.e. the three primaries. Hence the white light.

Any three coloured lights when mixed will produce a range of colours, known as a gamut. R, G and B produce the broadest gamut, which is why we know them as the additive primary colours. All the colours you see on your TV or monitor, including greys, are created by a mixture of those three.

You will often read that all colours can be made from R, G and B lights. This is incorrect. No three primaries can reproduce all possible hues in all values and all intensities. When we talk about primary colours we have to recognise that the RGB primaries are an optimal set that produces the most colours, not a perfect set that produces every colour. Other sets of colours you could try to use as primaries will be even less perfect.

Subtractive colour


When you use paint, you are starting with white and adding colours to get to black, i.e. as you add colours the result gets darker. This approach, also used in printing, is known as subtractive colour mixing because the inks ‘subtract’ brightness from white as you approach the absence of light that is black. In additive and subtractive colour mixing, the thing you are ‘adding’ or ‘subtracting’ is light. Ink is transparent, which means that when you look at a printed colour, it’s the paper underneath that is reflecting colour back to your eye.



For printers, it’s cyan, magenta and yellow that are the primary colours. Black is usually added as an additional ink to get a better, deeper black. Together they make the CMYK system (we use a ‘K’ for black because in printing the colour plates would be aligned with a ‘key’ or black plate).

Thanks to the material limitations of pigment and of art surfaces such as paper or canvas, painting and printing are not able to reproduce the millions of colours the eye can see. They and RGB can have lots of different gamuts, which is why designers have to beware colour mismatches when they produce a design on a screen which then has to be printed. It’s a bit like translating between languages.

Incidentally you may have noticed that which colours count as ‘primary’ depends upon the context. In light, it’s red-orange, green-yellow and blue-violet, generally called RGB; in psychology it’s red, green, yellow and blue; in printing it’s CMY plus K. It all depends on the context in which colour is being applied.

Colour models


RGB and CMYK are colour models: abstract systems that allow us to define colours as a set of numbered values. (There are other colour models such as HSL and Lab colour, but I’m not going to get into those.) A colour model uses three or four colours as primaries that combine to produce ranges known as colour spaces. No colour model is able to reproduce all visible colours.

Colour spaces began with the tristimulus values, developed in 1931, based upon the human eye and representing all the colours of the visible spectrum. The tristimulus model gave us the CIE XYZ colour space, which has served as a standard for many years and from which other colour spaces derive.

To be clear, we have:

  1. The millions of colours the human eye can see, i.e. the visible spectrum along with various non-spectral colours.
  2. The colours we can display on a TV or computer monitor by using technology that mimics the trichromacy of the human eye by using three RGB primaries. Practicalities of materials and cost-effectiveness limit the gamut compared to human vision. The technology supposedly offers millions of colours, but realistically it’s more like thousands.
  3. The colours we can reproduce in a painting or in printing using mixtures of pigments.

Trying to reproduce the colour sensations produced in us by light, when relying on phosphors on a computer screen or solid pigments made of ochre, carbon, oil, chemicals and so on, is a challenge artists have been wrestling with since the cave painters.

Conclusion


Colour adds greatly to the richness of how we perceive the world, and our ways of perceiving it are multiple and complex. Every context we find colour in raises its own issues of perception, range, mixing and so on. It’s important to note that human colour vision is still not perfectly understood. Our recorded observations date back to Aristotle, and we will no doubt continue to make new discoveries.

I see no need to go any further into the complicated physics and biology of colour, since you can paint without them. If you want more information I recommend two awesome websites to which I am indebted: David Briggs’ The Dimensions of Colour and Bruce MacEvoy’s Handprint. They do get technical but they are treasure troves for anyone interested in colour.

Thursday, 4 August 2016

A short introduction to light

In the next few articles I’m going to try and summarise the theory and techniques you need to paint a successful realist portrait in colour.

The world is a complicated place, and painting requires you to think of many different variables. There’s the local colour(s) of a sitter’s skin. There’s the intensity, direction, and colour of the light source(s) they’re seen in, including reflected light. There are the textures: the roughness of skin, the gleam of fingernails, the gloss of an eyeball, the weave of clothing. There is the colour of the environment, such as green walls or a yellow scarf, that can bounce into the colour of the skin. There are the contrasts of colour temperature between warm and cool. It can be daunting when you realise how much there is to learn, but it’s also the start of a fascinating process, so the best thing is to embrace it!

Our task is to try and understand how the world around us works. We’ll start by looking at the general theory of light, then colour. Obviously these are huge topics, so I will keep to the basics. If you’d like to investigate more deeply there are plenty of resources out there. You may like to revisit my articles on lighting the head and tone on the head.

The basics of light


Without light we would see nothing, and there would be no visual art. The entire visible world is light on form. Painting is the application of colours of different values to a surface or screen to recreate and interpret what light reveals to our eyes. It is useful therefore to understand a little about optics, i.e. the physics of light and how we perceive it.

Light is energy emitted from a source that could be natural, like the sun, or artificial, like a lamp. We may imagine light as rays that always travel in a straight line. When a ray of light hits an object, the ray can do three things. It can bounce off, it can be absorbed or it can pass through. These behaviours are processed by the brain into a mental image of the object: our visual world is the sum of countless rays of light, bouncing from the physical objects of the world according to an array of natural laws, and giving us information about objects’ local colour, their distance from us, their texture, the time of day, and lots of other things. As artists we have to be sensitive to the ways in which light plays upon objects.

When light bounces off an object and back to our eye, this is called reflection:



If the surface is smooth and shiny, like glass or polished metal, the light reflects at the same angle as it hit the surface – this is called specular reflection. (There are degrees of specularity depending on the material.) When the surface is not smooth, the uneven surface makes the light rays bounce back at various angles. This is called diffuse reflection or scattering


Light cannot pass through opaque (‘non-see-through’) bodies, but transparent or translucent ones do let it through to various degrees. Transparent objects – e.g. clear glass or pure water – allow light to pass through without much scattering so that objects on the other side can be seen clearly. Translucent objects – such as frosted glass or tracing paper – diffuse the light, so that objects on the other side are not clear.

Depending upon the material an object is made of, some light may bounce off it, some may be absorbed by it, and some may pass through it. The latter is called transmission.


When light passes from one medium to another where its speed is different, such as water, it bends. This is called refraction. The angle of the refraction depends on the material.



Shadow


Areas that aren’t hit directly by the light are less well lit, i.e. they fall into shadow.



The length of the shadow depends on where the light source is in relation to the object. Below, the light source has shifted and the length of the shadow gets shorter:



In real life, light rays often emanate not from a single point but from an area: the full surface area of a lamp, for example. The object may block rays of light from part of that area, creating a solid dark shadow (umbra), but not from other parts, thus allowing a certain amount of light past: this makes the shadow diffuse at the edges (penumbra). Precisely how sharp or blurry the shadow looks depends upon the interplay of the elements involved: the angle, surface area and intensity of the light, the size and material of the object, and so on.


This is why objects can sometimes appear to have a double shadow even when there is only one light source: the light is coming from various points on the light-source area.

Value


Value, also known as tone, is the term for how light or dark something is (whether in colour or not). Some objects bounce a lot of light off and appear bright, others bounce very little and appear dark. Value ranges from white to black:



As the bottom row illustrates, values are affected by the other values around them: every one of the inset grey blobs is the same value, but the one sitting on white seems darker than the one sitting on black. 

Value helps us to create the illusion of three-dimensionality. It is determined by the angle of a plane in relation to the light source. Objects are lightest where the light hits them directly, then get progressively darker as they turn away from the light source. It also gives an indication of distance: the further away an object is, the more information is lost in the atmosphere on the way to our eye, and the more pale and low contrast it looks.

Value works hand-in-hand with perspective. A cube seen side-on doesn’t tell us much about the form. When the cube is seen in three dimensions, value helps explain to us what is going on:


A flat plane is even in value, but a curved surface has graduated tones. Thus the way we use tone on an object tells the viewer about its form. By combining the even tones of flat surfaces with the graduated tones of curved surfaces we can depict any form.



The classic method of studying how light works on three-dimensional forms is to place plain white models of basic forms – sphere, cube, cylinder, and perhaps also a cone – on a white surface and observe them in the traditional artists’ light, i.e above, to the side and to the front.



Painting a still life of this sort may seem a literally colourless exercise, but grasping the relationship between light, value and form is so essential that classically trained painters often study value in tones of grey long before they learn to manipulate colour.

One of the most basic building blocks in the universe is the sphere. Suppose we place a sphere on a tabletop and shine a light upon it. When illuminated by a single light source, half of the sphere will be in light and half in shadow, because light travels in a straight line and can’t reach more than halfway around the sphere (right). The stronger the light, the more pronounced the divide between light and dark. This exercise gives us the classic sphere illustration you’ll find in most art books:



I’ll talk you through this illustration in the notes below. Please note that not everyone uses exactly the same terminology, although the behaviour of the light is the same.

The light side


The plane or area that directly faces the light source receives more rays than elsewhere and is the best lit. We can call this the centre light.

Not to be confused with this is the highlight. Contrary to what you will sometimes read, the highlight does not directly face the light source but is a reflection of it, off the object and into the viewer’s eye. Its location therefore depends upon the standpoint of the viewer. The highlight tells us a lot about the material of the object. A hard, smooth object produces a sharp, shiny highlight. On a duller or textured material the light gets scattered about, so the highlight appears more muted and diffuse.

The planes that are only partly hit by the light are called half-tones. These vary in value depending on how far they are turned towards or away from the light.

The dark side


Halfway around the sphere, the light no longer strikes the surface directly and the shadow area begins. This has two parts: a cast shadow and a form shadow.



Cast shadow 

When one object blocks the light from hitting another – in this case a sphere blocking the light from hitting the tabletop – it casts a shadow. The cast shadow varies in shape and value, but resembles the shape of the object that cast it. Generally, the further the cast shadow extends from the object, the more light can get into it and so the softer-edged and lighter it gets. The darkest part is at the crevice where the object meets the surface and hardly any light can get in. This is known as the occlusion shadow.

The cast shadow’s appearance also depends on the type of light. A small, bright torch will create a different shadow to sunlight on an overcast day.

Beginners often assume that a cast shadow is a dark, black shape. Look carefully and compare its values to others in the scene. They may be much lighter than you think, thanks to light that bounces into the shadow from the environment. In nature cast shadows are always slightly see-through. Even when it is very dark, you may want to lighten and/or soften it, to avoid distracting the eye or confusing a form. 

Form shadow 

The form shadow appears on the object itself where the planes turn away from the light source. It too can go through subtle gradations. We can interpret it in three parts: dark tone, core shadow and reflected light.



What I shall call dark tone is the shadow-side counterpart to half-tone. It is variable in value, but always darker than anything on the light side.

The core shadow (Andrew Loomis calls it the ‘hump’) marks the darkest area where the surface has turned away from the light source but is picking up the least light from elsewhere. It is useful for indicating the corners of the form. If there isn’t enough reflected light on the shadow side to produce a contrast in value, you may not see a core shadow, but you might include one in your picture anyway to help define the form.

Some writers mention the terminator: this is a term for the edge, sometimes merely notional, between the light and dark. The core shadow isn’t the same thing, as it is a dark shadow area of variable size that lies just after the terminator.

Assuming the object is not floating in space, a certain amount of light will bounce back from surrounding surfaces (such as the tabletop) and make the shadow side lighter. This is reflected light.



The object also takes on colour from surrounding surfaces:



In effect the surface itself becomes a light source, but if we allow this light to be too strong, the viewer’s sense of the form could get confused. Best keep it subtle.

The value and local colour of a form shadow will be primarily defined by the object; the value and local colour of a cast shadow by the surface it’s cast upon.

Shadow areas, as well as being darker than lit areas, also tend to have lower contrast and less intense colours.

An example


As an illustration of the practical application of all this, see below how Leonardo has applied some of these aspects of light to his drawing of a girl’s head. If you imagine the head as an egg, which is really just an elongated sphere, it is much easier to grasp.


Leonardo da Vinci: Head of a Girl (detail)

Closing notes


Exactly how an object looks at a given moment depends upon the positions of the light source and of the observer. If several people standing in a circle look at the same object in the same light, each will see something slightly different. Also, the precise disposition of light and shadow depends upon many variables. Most of the things you paint will not be spheres sat upon level tabletops. You will have to observe the intensity of the light, the amount and angle of reflected light, the materials objects are made of, and so on.

I will leave the final word to the outstanding drawing teacher Robert Beverly Hale:

The professional artist is acutely aware of the existence of light and its effect on form. He understands that light can create or destroy form: thus, he must be the creator and destroyer of light. He is instantly aware of light sources that play upon form: their colour, position, size, and intensity. He can change the position of these sources; regulate their colour, size, intensity; quench them; or create new sources.

He decides the number of lights to throw upon the form and knows the danger of throwing more than two. He decides with exactitude on the progression of tones. He is a dedicated hunter of cast shadows; he can spot one at a hundred yards and annihilate or tame it at a glance.
Drawing Lessons from the Great Masters

By all means observe and imitate nature, but you should not be in thrall to what you see. Be ready to edit nature if you think that your forms can be made clearer.


Wednesday, 6 July 2016

Planning a portrait

A portrait is normally an artistic representation of a person, attempting to capture both their appearance and an impression of their character. They can be made in any media and show the head, bust, torso or full body. Portraits have a very long tradition, valued for their documentary, social and symbolic roles as well as allowing artists to study the psychology of what it means to be a human being.

The invention of photography undermined portraiture’s role as the principal recorder of what individuals look like. But though the form is arguably taken less seriously today in the art world, its tradition is going strong. The human face, with all the diversity it offers, will always be intriguing to artists, some of whom dedicate entire careers to portraiture alone.

This article raises a few things to consider when setting out to paint a portrait.

Pose and composition


The artist wants to pose their sitter in the way that best communicates who they are. If possible you should meet him or her and get acquainted with their character, behaviours and typical environments. This sort of insight can help your decisions about how they should best be presented. Certain poses go with social conventions, status and expectations, but at the same time everyone has their own ways of carrying themselves and behaving, which can be intensely personal. The main dividing line is between formal and informal portraiture. The formal portrait may require a highly conventional pose, such as standing in one’s best clothes or sitting at a writing desk. The informal portrait can be much more spontaneous, in an everyday setting and featuring a more active facial expression – in the era of Instagram snaps we are probably more comfortable with this approach.

The subject may appear full-face or in profile, but a slight turn such as a three-quarter view is the most commonly used. You can combine it with an over-the-shoulder look like in Vermeer’s Girl With A Pearl Earring (right). Whatever you do, keep the focus of attention on the face, especially the eyes.

Should the subject look straight at the viewer, or look away? If he or she looks away, it could create a meditative mood, or it could invite the viewer to follow their gaze or ponder what they’re looking at, assuming you’re not showing us. If they look at the viewer, it immediately makes their gaze the focus of our attention. This can be powerful, even discomforting.

Our choice of pose ties closely with our sense of composition, as both are concerned with organising image elements on the picture plane. Early on you must decide on the size of the image, and whether to draw the head, the head and shoulders, or some measure of the body. If you include at least part of the body it will give you more material to work with, especially the hands as they can contribute to the overall flow of the composition and are particularly expressive. Or you may wish to give them something to do, such as an object to hold, like in Renoir’s portrait of Ambroise Vollard (right).

You may want to angle the shoulders rather than have them square, as they will probably be the widest part of the body and can help lead the eye into the picture. Bear body language in mind. A head tilted up can seem a bit challenging; a head tilted towards the lower shoulder can seem serious; a head tilted towards the higher shoulder can seem playful. If a person leans forward, they will seem engaged and interested; if they slump, they will seem muted or depressed; if they stand upright with legs planted apart and stare back at the viewer with hands on hips they will look very confident. Straight limbs can look stiff, so think of angling those joints in expressive ways. 

If you are drawing from a live sitter, make sure they are comfortable enough to hold the pose while you work, that their face is on a similar level to your own, and that they are not too far away for you to observe them closely. Six feet is a reasonable distance.

Your task is to work out how best to communicate a role and a personality through your choices.

Sketches


If you’re not sure what works best, draw quick little sketches of the subject in various positions, and to plan out your patterns of light and dark. Don’t begrudge the time. It’s better to take a bit of extra care at the beginning than to have a realisation halfway through a painting and abandon hours of work.

Working from a live sitter is better than working from a photograph because, as well as getting to know the sitter personally, you can walk around them, sketching and assessing your options.

Framing


Artists have used landscape formats and occasionally circles (known as tondi in the Renaissance), but the classic format for a portrait is an upright rectangle. Let’s take a look at a few pieces of good advice on positioning your sitter within the picture plane.

Full face


You want a pleasing balance of the head within the frame. Centre it vertically, but rather than putting it at the exact centre, shift it a little higher so there is more room below than above.

Show at least a bit of the shoulders to provide a base, otherwise it can look like the head is floating.


Three-quarter


In a three-quarter view, leave more space in front of the face than at the back. This gives a sense that the subject has a bit of room to move or gaze into.

Profile


The same principles apply in profile. Leave more space in front, again because it feels more comfortable. It’s best not to crop off the back of the head.

Close-up


Allowing the face to fill the frame is unusual. It lets the person dominate the picture and can be a powerful way to concentrate upon an emotion.

This is an example where cropping the head can work, as long as you’re doing it deliberately to achieve a dynamic effect.

Half-torso


Provided the sitter is only slightly turned away, a traditional guideline is that the sitter’s chin should be no lower than the centre of the picture area, and the inside corner of the nearest eye should be vertically centred.

If you show the hands, it's adviseable to show them in full, not to crop them at the wrist or chop off fingers.


Be wary of chopping off the top of people’s heads, especially at the hairline; and it’s better not to run a horizon line through the neck as if chopping the head off. Give your subject some breathing room, don’t cramp their head, and leave space for him or her to look into... Unless you have good reason not to take any of this advice.

The rule of thirds


The so-called ‘rule of thirds’, familiar to photography and cinema as well as art, is a technique for dividing the picture area in a manner pleasing to the eye. It was first documented by a minor artist in around 1797. It suggests using vertical and horizontal lines to divide the rectangle into nine equal parts, giving us four intersections.


We then try to align the important forms of our composition to the grid, with the focal points on the intersections. The idea is to avoid crudely cutting the picture in half or unthinkingly putting the subject bang in the centre, and that the eye naturally moves to the intersection points.


This method is widely used, and artists should be aware of it as it can help you reflect on your compositions and create a sense of balance.

However, it is just a handy guideline, not a universal truth. If your subject doesn’t fit the grid or intersections, it doesn’t mean your composition is wrong, and nudging your image sideways and upward to get the sitter’s face to coincide with an imaginary intersection won’t necessarily make the picture mysteriously better. A centrally placed subject can be highly effective, as in Caspar David Friedrich’s famous painting of a wanderer...


...and 99% of the oil portraits ever painted.

As for the eye naturally moving to the intersection points, there are other, more powerful ways to lead the eye, such as contrasts of light and dark, and compositional flow. Composition is another of those huge topics that would take a big series of articles to discuss, and I can't do it justice here. Suffice to say, you should treat the rule of thirds like any tool: use it if it helps you achieve your goals.

Lighting


Unless your creative intentions say differently, the best lighting is fairly gentle and comes from a single main light source slightly raised and to the left.


This is the most common lighting used in portraiture, as it has a balance of lights and darks that nicely reveal the forms of the face without distorting or confusing the features. Avoid strong shadows under the nose, lips and brow that will obscure the face. Intense light will expose every little crease in the skin and may make the subject squint.

Clothing


Clothing is more than an incidental covering. In a portrait, it can convey a great deal about the subject’s social status, context and personality. It’s perfectly sensible to advise that the clothing shouldn’t distract us from the sitter, but sometimes artists deliberately use vivid clothing as a centrepiece of a work, as in Ingres’ Mme Moitessier (right) where the elaborate dress fabric signals bourgeois ostentation. Suitably arranged, clothing also contributes to the composition. You can direct the folds to flow in certain directions to lead the eye, and you can use its colours to provide contrasts.

Materials fold in different ways, but avoid trying to show every little wrinkle, which can be distracting and unnecessary. Many portraits prefer full or partial nudity such as exposed shoulders and neck.

Background


Think about how you will handle the background. It may help to think of the background as negative space, i.e. space around and between the main subject that becomes a form in itself. Decide early whether it will be light or dark – dark backgrounds can be very dramatic. 

A popular approach is to place the sitter in familiar surroundings, such as their home, garden, or workplace. In the two portraits by John Singer Sargent below, we see a sumptuous interior and a conventional outdoor setting:

Left: Mrs Hamilton McKown Twombly. Right: Countess of Warwick and Son.

The alternative is to keep the background neutral, or indicate only a vague sense of setting. Either way it shouldn’t be so busy that it distracts us from the person.


Left: Portrait of Sybil. Right: Portrait of Robert Mathias.

In these two portraits, also by Sargent, the first has a neutral background, enlivened only with some dashing paintwork, whereas in the second Sargent has included a simple indication of the room that suggests a grand setting without going into lots of detail.

If a background is coming out too static or vertical, you could borrow a trick from photography and put the image at a tilt.

Using value and colour in backgrounds


Your main concern is how you can draw the viewer’s eye to the centre of interest, normally the sitter’s face. There are a few points to bear in mind. The sense of contrast for the whole painting is set by the background. If it is dark, the eye will be drawn to light areas; if it is light, the eye will be drawn to dark and/or colourful areas. The Baroque painters for instance, not least Rembrandt, understood very well the impact of a light face against a very dark background. A medium-value background can set up a contest between lighter and darker areas, which you can use to your advantage, but which could confuse the eye if not controlled. The stronger the contrast, the stronger the pull towards the head will be.

In the four examples above, see how Sargent uses hair, skin, clothing and background colour to create strong contrasts around the head. 

You can modulate the background’s relationship with the sitter by varying its values – a lighter area behind a sitter’s dark hair for example can provide a modest contrast that prevents the head from vanishing into the background. This is similar to the way rim light on the head works. A common device is to put the dark side of the face against a light background, and the light side against a dark background: this creates contrast and makes the head stand out more. Below on the left is a Rembrandt self-portrait from 1669. On the right is a version I manipulated to remove the lightening behind the sitter’s head. Note how much flatter that version looks, and how the headgear stands out less clearly:


Conversely the sitter might throw a shadow against the background, providing an area of darker value that could help create contrast. 

A longstanding technique for manipulating the pattern of value is vignetting. The principle is to draw the viewer in to the centre of interest by making the outside edges dark and the centre lighter, or to put it differently, by making the key directional elements of the painting (such as a shoulder or a flow of long hair) darker where the form is nearer the edge and lighter further in. Against a light background, the reverse would apply: the centre of interest would be dark for contrast and the edges lighter.

The sitter’s clothing also needs careful consideration. To minimise distraction, make it dark against dark backgrounds and light against light backgrounds, though with some change of value to differentiate it. In the Rembrandt above, the clothing is generally slightly darker than the dark background. (Note however how the clear line of the shoulder helps frame the important facial area for the viewer and provides a kind of directional arrow towards the face.)

If you use strong colours for clothing such as bright red, they will draw the eye, and may distract from the face. A way of neutralising this is to use the colour (or colours) throughout the portrait, so that it becomes a ‘norm’ against which the face is the area that stands out: if the sitter is wearing red, make the background red too, perhaps cooler or less saturated. Alternatively, use different kinds of contrast to keep the viewer interested in the face despite the attractive power of the coloured clothing. For an example, see Bronzino’s Portrait of a Lady in Green on the right. Bronzino has balanced the woman’s dress with a red background. Although these are strong colours, and complementaries, they share a very similar darkish value, allowing the light face and the white cloth on the bodice to stand out by contrast.

In the portrait of his wife below, Renoir chose to make background, face and clothing all quite similar in colour and value. The white figure is closely integrated with the white background. This is a more unusual strategy and makes the picture feel flat, but the one centre of strong contrast is, of course, where it matters: the head.


Using photography


Obviously photographs of your subject can very useful when you’re painting their portrait. They can capture spontaneous moments and expressions, and can serve as reference for an absent sitter. However, try not to copy them uncritically, because photographs record data differently to painters and can distort the subject in various ways. Feel free for example to adjust the patterns of light to suit yourself. It’s best if the reference photo is itself carefully taken, in good light and with attention to the final composition.

What to do 


If you are short of sitters and aren’t interested in making subjects up, you can follow the venerable path of the self-portrait. Sit in front of a mirror and experiment with poses, lighting types, backgrounds and so on.

A final word: good advice is based upon years of experience. But don’t let rules put you off doing what you want. Many of today’s rules are the daring experiments of the past.