Colour replacement therapy ..

It is some while since I shot the original images for the Colour assignment and much water has passed under the bridge since then.  Many more photographs have been taken and more opportunities have arisen to generate further pictures that I felt were better than my original submissions, even though the originals met with positive tutor response.  The images I have replaced were ones where I felt that the replacements were technically better or where I wanted to show colour combinations that were more part of a scene than some of the images I collected back in the spring.  I also wanted to add an extra colour accent in yellow as my original offerings were somewhat heavy on the red theme, and that is the first image shown here.

Yellow colour accent

The orange and blue complementary combination is now one of the shots I took on the recent OCA study visit to the Brighton Photo Biennial ….

Orange and blue complementary

… and the red and blue contrasting image has become ..

Red and blue contrasting

I certainly don’t intent to backtrack over all the assignments I have done so far and start to replace too many submitted images, as that would wipe out any traces of development (hopefully!), but I felt that it was warranted in this case as the number of set up static shots I had originally used was more than I was comfortable with.

Assignment 3 : Colour : Tutor feedback and response

The tutor response to Assignment 3 Colour has been received and I am delighted with the reply.  Not too much that I can add, but here are a couple of quotes:

 You have submitted a selection of sharp, correctly photographed subjects which clearly demonstrate that your comprehensive understanding of the basic principles of colour harmony is well founded.   Your selection is drawn from a variety of genres, namely landscape, buildings, flowers, close us and people.   You have not distributed your images evenly over the sixteen required but in my opinion this is not a serious drawback as the assignment brief does not specifically insist on that presentation.  Because your images are consistently correct it has left me with few comments to make other than to state my approval. 

In light of the comments regarding the spread of images across all the categories I decided to ensure that I did cover other options even though the tutor comment was that this was "not a serious drawback".  I don't want any drawbacks that I can help, so have added two images to cover green/violet and blue/violet as below to complete the set.  This required the removal of the second red/green combination to make space.

 My tutor also said "I am in the unusual situation of having very few comments to make because your work has been without errors.   You have created a set of very clear well saturated images from which a viewer would be hard pressed to misunderstand.   My remaining comment must be to encourage you to try to interpret all your forthcoming assignments to the same standards.

 He did comment that my three examples of colour accent were all based on red and that is something that I will now address with some other options before final submission for final assessment.  It was interesting that all the options I photographed during the run up to the submission of the assignment were all based on red;  I wonder whether this is because they are just more noticeable to me or whether there are more of them around?!

I have recently added an example of a yellow colour accent and deleted the pink cactus flower so as to expand the range of colours covered as suggested by my tutor.

Additionally I have removed orange/blue photograph of Cape Town and replaced it with an image taken during the OCA study visit to the Brighton Photobiennial as it was deliberately sought out to address the required colour combination.  It contained such a great assemblage of blue and orange I thought it was a far stronger image for final submission.

Another change was to add a blue/yellow combination, again a shot taken on a study visit, this time from the market outside the Saatchi Gallery.

 As far as the learning blog is concerned, his comments were:

You are maintaining your learning log to the same high standard as your assignment work.   You have taken on all the recommendations to obtain the benefits from a learning log by showing the results of the exercises, extending your studies by visits to art exhibitions in other fields than photography and expanding your background reading.   Your log is well organised and has provided me with some interesting reading.   As in the case of your assignment you have set a high standard, which, if maintained, should take you to a successful conclusion to your course.

Exercise 25 : Colour relationships

This exercise investigates the relationship between colours and examines the influence of their proportions.  The first part requires the capture of scenes or parts of scenes that have the following colour ratios:

Red: green                  1:1

Orange : blue              1:2

Yellow : violet              1:3

I elected to use different approaches to these and chose to set up a basic still life, again using the peppers, to cover 1:1 red:green.  Although this was a very simplistic approach, it gave me a further opportunity to examine the role of exposure in getting the ‘correct’ colour.  I went with f/22 to get a good depth of field in the peppers and after looking at several different exposures, worked with EV of -1.5 to get the colour as close as possible to ‘true’ red and green that I wanted.

A second attempt at red:green 1:1 came from a pair of poppies that I photographed in a roadside garden.  The intense red of the poppies showed well under the natural light although the green was a little muted as the leaves and grass behind were in shadow.

Orange:blue at a ratio of 1:2 was quite a difficult combination to find.  Some other students have used orange life belts and blue swimming pools for this option, although lacking either around here, I decided to use an image of a kingfisher for this one.  It was surprising just how many of these kingfisher images I’ve got that failed to fulfil the required ratio of colours!  I had not intended to start using any of my bird images in the OCA work at this stage, as I regard that as a separate area of my photography entirely, but there is a need to fulfil the brief and move on.

Yellow:violet with a 1:3 ratio is a shot of part of a violet flower.  It was shot using a Sigma 100mm f/2.8 macro lens and at f/11 to ensure that the undulations of the petal surfaces were in focus.

The second part of this exercise required the production of images with colour combinations that just appealed to me, and to take note of any tensions that were created with the combinations selected.

My first photograph is from the hull of the replica ‘Golden Hinde’ in London along the Thames embankment.  Whether the original boat ever had the clashing red and yellow paintwork is unclear but I thought it created a strong visual tension, exacerbated by the sharp and alternating lines which separated bands of each colour, as well as the fact that they were set against the black pitch side of the boat hull.  Red and yellow are separated in the colour circle by orange and create a strong contrast, often used in warnings and to make an eye catching and attractive visual statement.  Black backgrounds are also frequently found adding to the impact.

I think the most striking, and indeed visually violent, colour combination I found was on the South Bank in London and featured bright orange and yellow, with a splash of bright pink .. Orange and yellow are adjacent to one another in the colour wheel and have complementary properties.  I thought these did indeed go well together in this image, but the introduction of the lurid pink completely unbalanced the image in my view.  It was clearly intended to create a ‘can’t miss it’ impact to draw people to the ticket office, but I thought it was a great example of how colours that go well together can be completely dislocated by the introduction of a small area of another colour.  It really appealed to me, but not in a comfortable way!

My final photograph is of a series of coloured stars on a window with the reflection of the blue sky and London skyline in the background.  The colours appealed to me as they were quite muted, yet I felt were striking as a visual device to advertise Team London before the Olympics.  The blue and yellow are separated by green in the colour wheel and are therefore not complementary and may be seen as clashing in some situations.  I felt they went together well in the situation, helped by the muted tones of the colours themselves and also by the dominant blue of the background reflection.  The pink, or at least red, is also a third of the way round the colour wheel from the other two colours and again would be predicted to clash, although I think that they are complementary in this particular situation.

This exercise, or at least the first part, was more difficult than I had expected it was going to be.  Finding appropriate colours, whilst largely avoiding painted surfaces, is not an easy task, and I was surprised just how much of the world is grey, brown and a plethora of shades of green.  There is therefore a tendency to look towards set up situations and still life to address this exercise, and indeed several of the others as well.  Found situations with the right colours and ratios are hard to discover, even with careful thought and judicious cropping.  I had hoped to be more imaginative in my photographs and especially to try and settle on a specific theme as I had done for Elements of Design, but I had to widen the net to address the exercise. 

The value of red ...

Just a brief add on to my last post about the emotional and psychological impact of colour.  Somewhere amongst the Olympic fervour, I just spotted a rather interesting article on the BBC website about the emotions of red and why it is proven to be a successful colour in sports clothing ..

“The researchers had a straightforward explanation for why wearing red makes a difference. Across the animal kingdom, red colouration is associated with male dominance, signalling aggression and danger to others. The vividness of the red displayed by individuals of various species has been shown to relate to the amount of the hormone testosterone they have in the bodies, which also correlates with their physical health and eventual breeding success. The researchers claimed that humans too are subject to this "red = dominance" effect, and so, for combat sports, the athlete wearing red had a psychological advantage ..”

Colour and emotion

I thought it was definitely time I started to look at the impact of colour on how we feel emotionally.  Colour as a device to influence feeling has long been established in art, advertising, marketing and just about any phase of life where we might be susceptible to having our perceptions and feelings changed and many worthy papers have been generated on the subject by psychologists and others who would wish to influence us.  The Colour Affects  website carries a neat summary of the basic feelings associated with different colours and a personal synthesis of views from various sources (e.g. Freeman (2007) and Color Psychology) point at the conclusions I have drawn below.

Red has power and is the colour that takes attention of the viewer first as it has the property of appearing nearer than it actually is (never noticed the nearness thing – must check).  Obviously widely used in warning signs and lights.  It is negatively associated with aggression, defiance and stress and positively with warmth and strength and excitement and energy.  It is often linked with masculine symbols (Ferrari, Marlboro, Red Bull, McLaren to name but a few).   Red is used linguistically as well as visually to indicate strong emotion (e.g. red hot, red handed, see red etc.) so its perception covers several levels of human emotion.

Green is the universal colour of peace, harmony and tranquillity and has a refreshing psychological impact although it does have some negative connotations tending towards tedium and boredom.  The wavelength of green light is in the middle of the visible light spectrum and its restful and balanced qualities are attributed to this.  At a very deep psychological level, it has been suggested that green is the colour of growth and food and therefore has a calming effect at a fundamental human level.  There are linguistic connotations again here – actors relax in the green room, and negatively, green with envy.

Blue is seen as an intellectual colour and its positive associations see it used in advertising to offer efficiency and trust in business and finance and also with logic, calmness and coolness.  Its association with water also sees blue as reflective and serene and features extensively in advertising around certain holiday destinations and medications.  It is claimed that bright blues are stimulants to thought and paler shades influence concentration.  Much used by companies who advertise management consultancy and according to numerous Google sources, is always voted as the top colour in the world and features in more sports kits than any other.  However, on the negative side, it can also been seen as cold and unfriendly.  If you go to Colour Affects and complete the poll, you will find that blue was the favourite colour from over 340,000 people who have clicked the survey!

Passion, fun and sensuality are apparently conveyed by orange (strange then that it is the colour of the Dutch!!) as well as carelessness and lack of concern for impact.  Orange used with black is associated with particularly negative feelings and lack of gravity. 

Yellow is claimed to have a strong emotional effect and cause a psychological boost and outburst of creativity as long as it is the within the right tonal range and in association with the ‘correct’ other colours.  According to Colour Affects, get it wrong and your confidence and self-esteem will plummet.

Violet is the shortest wavelength (remember ROYGBIV from school  ?) and reputedly has spiritual qualities around awareness and ultimate truth – not sure I go for that, but it is widely referenced.  Negatively it is seen as a colour which gives feelings of negativity and feelings of smallness and insignificance.  It has strong associations with top quality and is widely used in various regalia associated with monarchy.  However, advertisers assert that overuse of violet/purple make people think of low quality and tacky products faster than any other colour, which is interesting.

There is a vast amount of information on colour available from books and the internet, and I have no intention of trying to produce an exhaustive treatise where many others have been before, but I did feel it essential to record a few thoughts on the emotional impact of colour at this point in my learning.  On reflection, it might have been an unwise choice to publish my blog in black and orange, so I hope assessors do not get overwhelmed with feeling of negativity, lack of gravity and violence as they read !!  I have no intention of tangling with the workings of Blogger at this stage to change anything, so I’ll just note the point and continue!!

Exercise 24 Primary and secondary colours

The exercise here demands that photographs are taken that show scenes or parts of scenes that are dominated by each one of the primary (red, yellow, blue) and secondary (green, violet, orange) colours.  It is suggested that exposures are bracketed by half a stop and the one that has the closest colour match to the intended output selected.  There is strong discouragement from exclusively photographing paint, the likely outcome of doing this exercise too rapidly, and really taking some time to search out more imaginative subjects to photograph.  There is a wealth of natural subjects as well as textiles, foods etc. to go at, and I hoped to work mostly with these as I progressed through the exercises and assessment options.

I had no particular theme in mind when I set out to conduct this exercise, and the resultant eclectic mix of subjects bears testimony to this.  It was immediately obvious that it is very difficult to just go out and find the right colours, both from the perspective of subject matter and from that of the great variety of colours that did not quite match what I was after.  There are clearly a large number of tones of each colour that fail to fit the true primary and secondary criteria, with green clearly being the most troublesome.

All the colours I have imaged were compared visually to the primaries and secondaries on a Gretag Macbeth colour calibration target card to get them as close as possible to the true colour.  I am using a monitor calibrated with an X-Rite Eye-One-Display-2 calibration device, and I am happy that the colours I am publishing are ‘correct’.   However, the compression applied to images in blogger is not convincing me that it does not alter colours, although I am confident that images put forward for assessment in my Flickr Pro account will be accurate.

I attempted to fulfil the exercise brief by taking pictures of a wide range of subjects, whilst avoiding paint as far as possible ...  For red I took some pictures of a number of different fabrics and finally selected a close up of a one day cricket shirt (complete with ball and logo to really labour the point!!).

For yellow I took a number of images of flowers, finally settling on this image of a group of primroses, photographed with an exposure compensation of -1EV, to give the most accurate representation of the yellow on the calibration card.

Blue is a shot I took in Shetland of a shag (yes, the bird really is called that ..) with the water behind lit to a stunning blue by the reflection of the sunlit wall of the Lerwick fish factory !  Interestingly, a very slight change in angle caused an entirely different effect as the blue reflection was disturbed by the waves that were running on the sea and the solid colour disappeared by moving only a couple of feet to the side.

For the secondaries, and for green, I had my only diversion into paint as an alternative to the endless options offered by green grass and leaves, and chose to photograph this vintage lorry at a local fair.  The green of the cab has an excellent fit to the true primary green on my colour calibration target.

Orange was represented by a winter sunrise over the Lambourn Downs where the sky and frosted grass turned a magnificent fiery orange as the sun cleared the horizon.  As an alternative, I did briefly consider a part of the London Eye that was painted orange, but in effort to avoid a paint image I have a strong preference for the sunrise.  I have shown both images here for interest.

Violet was probably the most difficult to find, although there were a number of flowers that fitted the bill.  I photographed a number of irises and pansies, finally deciding to go with the predominantly violet close up of one of the iris flowers.  This image also has a proportion of yellow in it and may feature at a later date when I need to show some pictures which adhere to defined colour ratios.

This exercise on primary and secondary colours was not quite as easy as I expected it to be.  This was due in part to the endless dismal weather which was not conducive to the outdoor natural light photography I had largely planned, but mostly attributable to my underestimating how time consuming it would be to find apparently simple colours without resorting to painted surfaces.

Ian Cameron - Landscapes and Colour

At the end of my assessment feedback for Elements of Design my tutor suggested that I might look at the work of landscape photographer Ian Cameron to see his use of colour in preparation for the Colour projects building up to Assessment 3.  Ian’s website Transient Light, shows a wide variety of his images and also his interesting comment that some observers have found his work  to be‘saccharin sweet’, presumably because of the intense colours that he portrays in his images – but that was just what I was looking for. 

I got hold of a copy of Cameron’s book ‘Transient Light – A photographic guide to capturing the medium’ and have also been in contact with the author to enquire if I could use some of his images in my blog post to avoid having to talk about pictures which can only be linked – I have a thing about  this .. if I am talking about a particular image I want it here and not linked elsewhere, which was why I felt I had to start the hardcopy learning journal.  Ian replied that I could use some images if I linked to his site in the text and displayed his copyright, which was excellent news. 

Many thanks to Ian Cameron for kind permission to replicate the images from his website.  All images are copyright of Ian Cameron.

I intended to use a landscape image or two in the exercises around primary and secondary colours, and Cameron’s Findhorn Twilight has some spectacular oranges.

Findhorn Twilight  Copyright Ian Cameron.  Used with kind permission.

A superb violet/orange combination comes from Lavender Twilight, an image taken from a commercial lavender production site in France.  Probably not quite the classic violet I’m looking at on my colour card, but not too far off ..

LavendarTwilight   Copyright Ian Cameron. Used with kind permission.

Much of Cameron’s work focuses on dawn and dusk and there are therefore a multiplicity of examples of oranges and reds, all taken at the decisive moment (heard that before ..) when the light is perfect .. hence transient light of course.  Another great example of oranges is Slot Sculpture 4 taken in Arizona in the USA where the light colours the sandstone to perfect orange hues.

Slot Sculpture 4    Copyright Ian Cameron. Used with kind permission.

A blue comes from Palm Beach, taken in Zanzibar, with the stunning sky being a perfect colour.

Palm Beach    Copyright Ian Cameron. Used with kind permission.

Finally, Tea Plantations from Malaysia was another striking image that delivered superb greens. It also gives a fine example of red and green in an image, although not in the 1:1 ratio I need to find !!

Tea Plantations    Copyright Ian Cameron. Used with kind permission.

I could go on at some length about the website and the book and the images they show, and I would highly recommend both as examples of landscape photography and the use of intense colour derived from naturally lit situations.  It is certainly something I need to remember as I progress through Colour in TAOP and later in the Landscapes unit of the course.  When I come to that I can only hope for some decent weather and light – I would certainly not want to be doing the unit this summer!!

Exercise 26 : Colour into tones in black and white

I was intrigued in Assignment 2, Elements of Design, at the impact that removing colour from an image actually had in terms of changing the focus of attention within an image.  All my London shots were obviously taken in colour and I converted a good many of them to black and white once I had decided that this was the best way to explore design elements without getting diverted into colours and altering the perception of an image.  Exercise 26 explores this same concept to a degree and calls for a still life image composed of red, green, yellow and blue to be converted to black and white and then digitally filtered to explore how each colour changes and can be emphasised or suppressed by tonal control.  The options here are vast given that each colour can be adjusted over a huge range of shades of grey.

Although I have so far avoided using the same examples as are used in the OCA course notes, I have on this occasion chosen to work with a collection of peppers of red, yellow and green colour, set on a blue background, much the same are used in the notes.  I initially set up the shot with a grey card (not shown) exposed to appear about 18% grey and took a single image under natural lighting with a simple white foamcore reflector placed to minimise shadows around the peppers.  The camera was on a tripod and the exposure taken at f/22 to maximise depth of field of the subjects.  The image was converted to black and white in Lightroom 4 and then replicated to generate the other images upon which to perform the colour ‘filtration’.  The replicate images were processed with the Lightroom presets

The initial colour version and unaltered black and white conversion are shown below.

Original colour image

Default black and white conversion

The simple conversion has preserved the ‘strength’ of the original colour image, with the yellow appearing as the lightest colour and green the darkest. 

The red filter preset radically changed the tonality of the red pepper and caused it to become a lighter black and grey subject whilst darkening the tone of the green and yellow peppers (yellow is not so obvious in the compressed blog image, but is very clear in the original).

 

Green filtration significantly darkened the green pepper and lightened the red and yellow, and the blue preset lightened the blue background whilst making all the peppers go dark grey.

 

Application of the yellow filter made the yellow pepper go almost white whilst the similar green pepper became much darker in tone.

I’m really getting into black and white and I’m fascinated by how easy it is to completely change the character and impact of an image by simply converting to mono and then using the colour sliders to adjust the tones of the greys in the resultant photographs.  It’s certainly something that I will try much more of in the future.

Exercise 23 : Control the strength of a colour

The first exercise in the Colour projects deals with how exposure settings can control the strength of colour in a photograph and requires that five photographs of a subject with a strong, single colour are taken at different exposure values.  The single colour is needed to fill the entire frame of the pictures and the frame ideally should not move between exposures, so I set this up on a tripod, using a bright red backdrop and a cricket ball.

In my usual shooting mode of Av (aperture priority), altering the f-stop would result in the shutter speed changing automatically to maintain the ‘correct’ exposure according to the cameras metering system.  It was therefore necessary to set the camera to manual so that the same shutter speed was maintained and only the aperture changed – obviously this is going to result in over and under exposure.  The camera metered the subject that I selected for this exercise as 1/350 sec at f/5.6, so I took the first exposure at this setting.  With manual mode then selected I took further images at f/4 (so at a wider aperture than the metered setting), and at f/4.5, f/5.6, f/6.7, f/8 and f/11, all at 1/350sec.

These photographs were imported into Lightroom 4.1 and examined in their RAW state without any manipulation or correction.  Increasing underexposure gave an increasing strength of colour as can be seen from the sequence of photographs presented below.  Using LR to mouse over the same point of each image allowed the RGB values to be recorded; these were as follows, and it is interesting to note that the R:G and G:B ratios remain fairly constant throughout the series of images.

f-stop  Red     Green Blue

f/4.5     71        44        37

f/5.6     61        35        28

f/6.7     53        30        25

f/8        42        23        19

f/9.5     34        18        14

f/11      27        11        8

Freeman (2007) in The Photographers Eye (p106) discusses the value of over and under exposure in either diffusing or concentrating attention of the viewer, and shows how intentional underexposure can be used to focus on specific bright elements of an image and restrict the eye from wandering away from the prime purpose of the photograph.

I took this exercise one step further and used a sequence of images I had taken previously allowing the camera to make its own adjustments to exposure as I stopped down the aperture from f/5.6 to f/22 to demonstrate just how technically efficient the metering system is at remaining almost identical colour as the settings changed (aperture and shutter speed in the instance).  It is the bonnet of a Lamborghini (unfortunately not mine ..) and appears in the sequence of images immediately following those for exercise proper.  Mousing over the same spot on each image in the sequence demonstrated almost zero variance in numerical RGB values.

It is worthy of note that brightness and saturation are often mixed in photographic interpretation and it needs to be recognised that they are not the same thing.  Changing the exposure, as in the exercise here, will alter the brightness of the colour in the images, but the actual purity of the colour itself will not alter.

This struck me as quite a formulaic exercise when I started, and I don’t really get inspired by the “do this, now do that” approach, but I think I got quite a lot out of it once I had the images in front of me and the chance to look at impact of changing the f-stop and the impact of that in turn on the numerical RGB data.  I chose red because that was what was most easily accessible, but I plan to return to this and repeat it with a couple of other colours to see what that turns up.

f/4.5 and 1/350sec

f/5.6 and 1/350sec

f/6.7 at 1/350sec

f/8 at 1/350sec

f/9.5 and 1/350sec

f/11 and 1/350sec

f/5.6 at 1/750sec in Av mode

f/8 at 1/350sec in Av mode

f/11 at 1/180sec in Av mode

f/16 at 1/90sec in Av mode

f/22 at 1/45sec in Av mode

Colour theory - an overview

I thought at this point it was worth considering what makes colour and how we perceive colours.  Michael Freeman, in the OCA course notes, and in the additional material to be found in ‘Colour Theory’ on the OCA website, gives an overview of this but I wanted to explore things in greater depth.

Colour vision is the capacity to visualise objects based on the wavelengths (frequencies) of the light they reflect, emit, or transmit. Perception of colour by man is a subjective process whereby the visual cortex in the brain responds to stimuli produced when light enters the eye.  Hence, we all perceive colours differently to a degree.

The components of light have been known for several centuries. In 1670 Isaac Newton discovered that white light splits into its component colours when passed through a prism, but that if those individual spectra of colored light are subsequently passed through another prism and rejoined, they made a white beam. The characteristic colours are, from low to high frequency, red, orange, yellow, green, cyan, blue and violet. Sufficient differences in frequency give rise to a difference in perceived hue; the just noticeable difference in wavelength varies from about 1nm in the blue-green and yellow wavelengths, to 10nm and more in the red and blue. Though the eye can distinguish several hundred hues, when those pure spectral colors are mixed together or diluted with white light, the number of distinguishable chromaticities has been estimated to be up to ten million, although estimates and their scientific derivation vary according to source.

Colour is often mistaken as a property of light when it really is a property of the brain. Our experience of colour depends not only on the wavelength of the light rays that hit the photoreceptive retina, but also the context in which we perceive it. The background, lighting, familiarity of the situation, and surroundings of an individual can all impact on the precise colour that the brain interprets from the visual information it receives.

Within the retina are receptor cells called rods and cones. When light energy strikes them, neural signals are created as a result of chemical changes. The signals are then routed through neighbouring bipolar and ganglion cells that form the optic nerve which transmits information to the brain's visual cortex. 120 million rods are responsible for human perception of black, white, and grey and are the most sensitive in dim light. Only 6 million cones enable us to see colour and fine structural detail. They function in well-lit conditions and become ineffective with diminished illumination. In very low light levels, vision is termed scotopic and light is detected by rod cells of the retina. Rods are maximally sensitive to wavelengths near 500 nm.  In brighter light, such as daylight, vision is termed photopic and light is detected by cone cells which are responsible for color vision. Cones are sensitive to a range of wavelengths, but are most sensitive to wavelengths near 555 nm. Between these regions, mesopic vision comes into play and both rods and cones provide signals to the retinal ganglion cells. The shift in color perception from dim light to daylight gives rise to differences known as the Purkinje effect.

There are three primary colours - red, blue, and green - that make the millions of colours that are distinguishable by the "normal" human eye. Each eye contains three receptors (one for each primary colour) that generate the experience of colour when stimulated in various combinations. This is known as the Young-Helmholtz Trichromatic Theory. Those who have defective cones have difficulty seeing certain colours and are known to be colour-deficient or colour blind.  With this in mind, it is fair to then say that the number of colours the human eye can discriminate depends mainly on the sensitivity of the individual's eyes. The monochromatic colours of the rainbow (red, orange, yellow, green, blue, cyan, and violet) have their wavelengths in the 480-740nm range. When light strikes an object, it can be absorbed, reflected, or scattered and when the surface absorbs all wavelengths equally, we perceive it as black and when the surface reflects all wavelengths equally, we perceive it as white

Visible light is an electromagnetic wave that has a wavelength range of approximately 380 nanometres to 740 nanometres as shown below.

Colour	Wavelength Interval	Frequency Interval
red	~ 625–740 nm	~ 480–405 THz
orange	~ 590–625 nm	~ 510–480 THz
yellow	~ 565–590 nm	~ 530–510 THz
green	~ 500–565 nm	~ 600–530 THz
cyan	~ 485–500 nm	~ 620–600 THz
blue	~ 440–485 nm	~ 680–620 THz
violet	~ 380–440 nm	~ 790–680 THz

We often use the HSB, or Hue, Saturation, and Brightness, model to classify colours. The hue of a colour is the particular shade or appearance of a colour. There are 150 hues the eye can distinguish and they include the colours of the visible light spectrum. Brightness refers to the amount of light emitted by an object and saturation is the purity of a colour, or the intensity of a hue. A less saturated colour would be more dull, while a highly saturated colour would be more vivid. The graphic below displays the saturation levels of the colour red, where the bottom has the least saturation.

There is often confusion between the behavior of light mixtures, called additive colour, and the behavior of paint or ink or dye or pigment mixtures, called subtractive colour. This problem arises because the absorption of light by material substances follows different rules from the perception of light by the eye.

A second problem has been the failure to describe the important effects of strong luminance (lightness) contrasts in the appearance of colors reflected from a surface (such as paints or inks) as opposed to colors of light; "colours" such as browns or ochres cannot appear in mixtures of light. Thus, a strong lightness contrast between a mid-valued yellow paint and a surrounding bright white makes the yellow appear to be green or brown, while a strong brightness contrast between a rainbow and the surrounding sky makes the yellow in a rainbow appear to be a fainter yellow, or white.

Colour theory was originally formulated in terms of three "primary" or "primitive" colors—red, yellow and blue (RYB)—because these colours were believed capable of mixing to produce all other colours. This color mixing behavior had long been known to printers, dyers and painters, but these trades preferred pure pigments to primary colour mixtures, because the mixtures were too dull (unsaturated).

For the mixing of colored light, Newton's colour wheel as shown in the course notes is often used to describe complementary colors, which are colors which cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colours exactly opposite one another on the hue circle cancel out each other's hue.

Colour theory has ascribed perceptual and psychological effects to this contrast. Warm colours are said to advance or appear more active in a painting, while cool colours tend to recede; used in interior design or fashion, warm colours are said to arouse or stimulate the viewer, while cool colours calm and relax. Most of these effects can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments.

Gestalt appears again in the study of the importance of colour, its recognition and in how the eye moves around a photograph.  The Gestalt Laws of Organization have guided the study of perception of visual components as organized patterns instead of different parts. As I have blogged in an earlier post, there are six factors that determine how the visual system groups elements into patterns: Proximity, Similarity, Closure, Symmetry, Common Fate (i.e. common motion), and Continuity