In visual perception a color is almost never seen as it really is – as it physically is. This fact makes color the most relative medium in art.
Albers Interaction of Color 1963 p1
Colour can only exist when three components are present: a viewer, an object, and light. Our perception of colour depends on both physical factors relating to the way the eye registers light and more psychological and cultural factors that affect the way the brain reacts to and interpretes colours and their relationships to each other. Artists and designers have used and experimented with complexities and ambiguities in interactions between physical and psychological dimensions of colour to portray emotions and question the nature of perception.
Key colour issues in printmaking
- Tone is perceived first, then colours (yellow first), and then the image. This means that the underlying tonal shape structure of an image is of primary importance. Using flat primary colours will detract attention from the image – making colour the subject.
- Hue is inherently problematic. The effects of mixing different pigment hues will vary depending on issues like transparency, saturation, value. Artists may choose to focus on local or optical colour.
- Optical mixing occurs as the brain interpretes colours, successive and simultaneous contrast. So perception of hue will depend on the relationship between elements in the composition.
- Colour responses in terms of perception, meaning and emotional response is a complex combination of hard-wiring of human perception, biological variation (eg colour-blindness) between different viewers and cultural associations.Or use completely arbitrary colours to impose their own feelings and interpretation onto the image.
Physical properties of light
Light consists of rays of different wavelengths. When light strikes a surface, certain wavelengths are absorbed and others are reflected by its pigments. Different combinations of reflected wavelengths form all the observed colours. Although pure white light is perceived as colourless, it actually contains all colours in the visible spectrum. When white light hits an object, it selectively blocks some colours and reflects others; only the reflected colours contribute to the viewer’s perception of colour.
Virtually all our visible colours can be produced by utilizing some combination of the three primary colours, either by additive or subtractive processes.
Naturally occurring colours are not just light at one wavelength, but actually contain a whole range of wavelengths. A colour’s “hue” describes which wavelength appears to be most dominant. The object whose spectrum is shown below would likely be perceived as bluish, even though it contains wavelengths throughout the spectrum.
Although this spectrum’s maximum happens to occur in the same region as the object’s hue, it is not a requirement. If this object instead had separate and pronounced peaks in just the the red and green regions, then its hue would instead be yellow (see the additive colour mixing table).
Biology of the eye
The human eye senses this spectrum using a combination of rod and cone cells for vision. Rod cells are better for low-light vision, but can only sense the intensity of light, whereas whilecone cells can also discern color, they function best in bright light.
Three types of cone cells exist in your eye, with each being more sensitive to either short (S), medium (M), or long (L) wavelength light. The set of signals possible at all three cone cells describes the range of colours we can see with our eyes. The diagram below illustrates the relative sensitivity of each type of cell for the entire visible spectrum. These curves are often also referred to as the “tristimulus functions.”
|Select View:||Cone Cells||Luminosity|
Raw data courtesy of the Colour and Vision Research Laboratories (CVRL), UCL.
Cambridge in Colour: Colour Perception
Note how each type of cell does not just sense one colour, but instead has varying degrees of sensitivity across a broad range of wavelengths. Move your mouse over “luminosity” to see which colours contribute the most towards our perception of brightness. Also note how human colour perception is most sensitive to light in the yellow-green region of the spectrum; this is utilized by the bayer array in modern digital cameras.
Eye to brain
As light passes into the eye it strikes the retina at the back of the eye which consists of layers of cells including:
- rods – that perceive black and white and allow us to see dimly lit forms
- cones – that help us perceive hues. The cones in the eye only recognise red (long wavelengths), blue-viiolet (short wavelengths) and green (middle wavelengths). They relay these colour messages to the cones of the fovea, an area at the centre of the retina, whose cones transmit to the brain.
The brain then assimilates the red, blue-violet and green impulses and mixes them into a single message that informs us of the colour being viewed.
There are many factors affecting our perception of a colour, such as the surroundings of the object, its surface texture, and the lighting conditions under which it is seen. How much of a colour is used, whether it is bright, dull, light or dark, and where it is placed in relation to another colour are also crucial factors in our perception.
– local colour: the wavelengths that are reflected by a surface under consitions of white light
– optical colour: the combination of local colour with light striking it and other surrounding colours
Subtractive processes are more susceptible to changes in ambient light, because this light is what becomes selectively blocked to produce all their colours.
COLOR PROPERTIES: HUE & SATURATION
Color has two unique components that set it apart from achromatic light: hue and saturation. Visually describing a colour based on each of these terms can be highly subjective, however each can be more objectively illustrated by inspecting the light’s colour spectrum.
A color’s saturation is a measure of its purity. A highly saturated color will contain a very narrow set of wavelengths and appear much more pronounced than a similar, but less saturated color. The following example illustrates the spectrum for both a highly saturated and less saturated shade of blue.
|Select Saturation Level:||Low||High|
Dimensions of colour
A colour without any black, gray, white or complementary is called a pure hue and occurs in Newton’s light spectrum. Primary colours are those which cannot be mixed using other colours, secondaries the result of mixing two primaries and tertiary colours, the result of mixing secondaries with one of their adjacent secondaries. Broken hues are the result of mixing these pure hues with their complement to produce browns and greys.
However there is significant variation between colour theorists as to how they identify primary colours, and also between additive methods (RGB used where light is added and where white is the result of mixing all light wavelengths) and subtractive methods (CMYK and pigment mixing as in printmaking or paint where black is the result of mixing all colours).
Moreover pigments are rarely pure. The results from mixing also depend on the relative colour temperature of each of the colours being mixed.
Pure hues vary in value from yellow (lightest) to violet (darkest) This means that when mixing them it will also alter the value. If you squint when looking at two hues of similar value they will merge together. When pigments of equal value are mixed together this gives a darker value because more wavelengths are absorbed and fewer reflected.
Value changes convey texture, are used for shadows and form. Sharp contrasts in value produce the effect of precision, firmness, objectivity and alertness. Close values produce feelings of haziness, softness, quiet, rest, brooding etc. Dark compositions give feelings of night, darkness, mystery and fear. Light compositions of illumination, clarity and optimism. Middle values are relaxed and often go unnoticed.
Discords: when the value of a hue is altered by the addition of black, white or another colour opposite to its natural value order eg adding violet and white to make lavender.
intensity (also termed saturation or chroma) defines the degree of purity or brightness (as opposed to light) or how dull (as opposed to dark) a colour is. Pure hues are those where there is no black, white or complementary colour added.
When pure black or pure white are present they are notices before the other hues and colours present.
Pure hues differ in chroma strength – lighter hues have stronger chromatic strength.
Pure hues can be dulled to coloured greys through adding grey of the same value. Or mixing with complementaries to produce a shade.
Neutral greys can be obtained through mxing false pairs – orange and green, green and violet, violet and orange. But they tend to favour one of the parent hues and are less powerful than those made by combining complementary hues. They can also be produced through layering.
Intensity can create effects on objects in space.
– high intensities make an object seem large and pushes it forward in the visual field
– light pure values like yellow advance most on a dark background and least on a white background
– pure hues have a relative strength. if balance is required, they should be used in the right proportion.
Temperature refers to the warmness or coolness of colour.
– Warm hues are yellow, yellow-orange, orange, orange-red, red and red-violet.
– Cool hues are
Certain colours relax us, others stimulate us.
Memory, experiences and cultural background all affect the way a colour’s impact can vary from individual to individual.
Factors such as linguistic distinctions can even affect perception of colour – in some languages there is no distinction between blue and green and so although people can distinguish when questioned they do not make an immediate distinction. Even where colours are perceived similarly, they may mean different things – in Asian cultures white is associated with death. Red is associated with happiness and luck. In Western cultures black is associated with death and white with purity. Red is associated with danger and blood.
influenced bybthe types of pigments available and their value.
blue lapis lazuli for the madonna
purple mollusc in ancient greece so royalty
ochres and earth colour
red vermillion marriage and luck in asian cutures
black terry frost absorbs all other colours. means a kind of depth. malevich black square
white purity. turns away other colours.
Artists may choose to focus on local or optical colour. Or use ciompletely arbitrary colours to impose their feelings and interpretation onto the image.
In reverse order of contrast:
a single hue with its tints and shades produced by mixing with white, black (or its complememtary?)
three or more hues that are next to each other on the colour wheel. Analogous schemes are most emphatic when the common hue is primary. They are most harmonious when the middle hue is primary (eg red-orange, red, red-violet rather than orange, red-orange and red).
equidistant on the colour wheel. These result in a dominance of warm or cool.
where the hues are equidistant on the colour wheel.
Itten and Albers studied the interaction between hues and the ways in which our perception of hues and tones is altered radically by the other colours surrounding them.
Vibration where certain hues meet.
Bounding with white or black.
Disappearing boundaries: where analogous hues meet
Dissolving boundaries: where broken hues meet
This can be used to create mysterious effects. Or combatted using sharp edges.
Discords play a supportring role – they are easily overshadowed by colours that are not discorded, but they stop the tendency of hues to spread visually. Large areas in discorded colours should be avoided as they weaken a composition. But small areas reduce monotony. Light discors also produce the best highlights (because they are unexpected and attract attention??) The discord chosen should be based on the primary colour closest to the object featured in the hightlight, or the next closest primary on the coliur wheel.
When colors or shades of grey are sequenced in a composition eading from ligt to dark or dark to light then the eye is comfortable. But when the esquence is broken eg gray background, followed by white then black then the effect is jarring eg dramatic skies. El Greco View of Toledo.
Rhythm, repetition and movement
Repeating colours can lead the eye through a composition and create a sense of movement.
Emphasis can be accomplished by using colour in a number of ways
– colour contrast: bright/dull, light/dark, warm/cool
– area size: large areas of a colour versus small
– texture: rough versus smooth
– use of arbitrary colour
– unusual detailing
– contrast with surroundings
Harmony can be achieved through:
– use of tonality
– surrounding a colour with a neutral colour
In printmaking, particularly relief prints, there is clear colour separation on the printing plate. This can use either layering and mixing, or optical mixing through juxtaposition.
Cambridge in colour – technical notes on colour perception, colour harmony and colour management for photographers.