Colour Theory for photographers

Introduction

Have you ever had a colour crisis?  Let me explain.  The judge on the night said “it would have scored a 10 except that I mounted it in a red frame which was not complimentary” and she went on “I would have to drop the score to a 7 or you will never learn not to do it again”.  Inside my head I was thinking “What’s wrong with it?”  I know that it’s always a risk using the red frame.  Roger Lancaster had a few prints in red frames.  One judge loved it, another hated it.  Is it safer just to stick with neutral black or white frames?  Are red frames definitely out?  The judge in question claimed to be an artist.  Has she got a more highly developed sense of colour than me?  Is she biased?  Is this just discrimination against red frames.

Perhaps it might be helpful to understand a bit of colour theory.  I will start with some basics.  Feel free to skip this part if you know it already.

What is colour?

Would you believe there are two answers to this question.

Spectrum

Sir Issac Newton wrote his seminal book, “Optiks”  on the properties of light, demonstrating that white light could be split into different colours as it passed through a prism.  Each colour could not be split further by passing it through further prisms.  He concluded that white light was a mixture of all of the colours.  Of course there are also non visible frequencies of light, like ultraviolet and infra red, x-rays and so on.

 

Light dispersion of a mercury-vapor lamp with a prism made of flint glass
Picture Source

Perception of colour by the eye

The eye has 4 receptors that can respond to light.  We perceive colour by comparing the signal from the 3 main colour receptors to determine which frequency / mix of frequencies we are seeing.

So colour is firstly the frequency of light, and secondly it is the perception of colour by our eye that has just 3 colour receptors.  It is the second definition of colour that gives rise to the theory of colour.

Mixing colour

When we see the colour purple in a rainbow we are looking at pure violet light (400nm).  However when we go to paint a rainbow we may mix red (650nm) and blue paint (450nm) to deceive the eye that we are looking at violet(400nm).   This is because the violet end of the spectrum is detected by both the blue and red cone in our eye.  Colour theory states that if we have just three colours that correspond to the maximum sensitivity of the three cones,  we can create the impression of the whole range of visible colours.  This is how your TV works.  These colours are known as the primary colours and are red green and blue.  This can be represented on a colour wheel where you slowly blend the three primaries to create a whole spectrum of colours.  It kind of looks like a rainbow where you joint the red and violet ends of the spectrum together.  The colours midway between the primary colours are known as the secondary colours.  They are Magenta, cyan and yellow.

Goethe,_Farbenkreis_zur_Symbolisierung_des_menschlichen_Geistes-_und_Seelenlebens,_1809

Goethe’s colour wheel 1809 (Picture source)

There is a fundamental difference between your TV monitor and a painting.  The TV monitor projects certain light frequencies at your eye.  The Painting reflects light back to your eye after absorbing certain frequencies.  One is additive, the other subtractive.  The dynamics are opposite to each other.  If you mix all colours on the TV you get white.  The absence of colour is black.  With painting it is the reverse, all colours create black and no colour is white.  Likewise, with painting the primaries are the reverse to the colours of the TV monitor.  The painting primaries are Magenta, cyan and yellow.  (Note these are the colours of the inks in your digital printer)

Muted colours – tints shades and tones

th5Q6U5EXWBut where on the colour wheel do I find duck egg blue and avocado green and burnt umber.  In fact there seem to be no browns.  It is not like the dulux paint guide, it is hardly a guide to all colours.  Duck egg blue can however be created by mixing red green and blue light in the proportions Red 78.8%, Green 91%, and Blue 87.8%.  I guess it is more green than blue.

If I was to try and make duck egg blue by mixing paint, I would first mix blue and green, giving a hue on the colour wheel (below left), then I would mute it by adding the opposite colour, namely red (below right).     In the diagram you can find something approaching duck egg blue at around 1 oclock on the second, the muted colour wheel.

color-wheel-game-new-gamboge-speedball-red-joe-blue-phthalo-chris-carter-artist-051212-web

Left colour wheel – right colour wheel muted by adding the opposite (the complement) (Picture source)

This process is emulated on the computer.  There is a colour system that describes colour as a value for the hue (position on the colour wheel), a value for the degree of muting (saturation) and a value for how dark or light the colour is (value or luminence).  On the computer this has two manifestations, HSV and HSL. I won’t go into the differences here.  However the HSV and HSL systems are a more intuitive and easier system for handling colour than by tinkering around with the rgb values.  It emulates the process you would use when you are painting.

The terms tint, shade and tone refer to how a colour is muted.  I tend to think of the paint shop.  If I want my duck egg green to go on the walls of my house I buy a can of white paint and add pigments to get the correct colour. This is called a “tint”.  If I bought a can of black paint I would be adding a “shade”, and if a can of grey paint a “tone”.  Likewise if I start with my colour wheel colour, you can add white black or gray to mute it, with the same terminology.

Of course colour blind people see things differently, as may do some animals and birds who have different colour receptors to our own.  They may not see all the subtlety of this blending and think our painting is just rubbish.

Contrasting colour

It is widely know that if you place a colour next to its opposite on the colour wheel that it produces a striking effect.  The transition between the colours seems to sparkle and shimmer.  One colour activates one set of cones (say red and green), the other colour activates only the remaining cones (blue).  It’s the zebra crossing of the colour world, like black against white.  This is often used both in nature and design to create strong colour contrasts.  If you think about it, with only 6 main colours,  there are just 3 pairings that create strong contrast, blue against orange, purple against yellow and red against green.  These pairings are used by designers to create colour harmony in design.  they are called complimentary colours.

colour contrast

Colour harmony and design

In fact designers have explored many ways of pairing and grouping colours to create harmonious combinations.

Colour harmonies

In summary you either use the same hue at different intensities (monochramatic) the opposite (complementary colour), or similar colours (analagous colour), or combinations of these as illustrated above.

You can down load an app for your phone.  “Colour Harmony” or “Colour Grab” are two examples.  You point the phone camera at your bare wall to capture the colour, and the app will select harmonious colours to use for the woodwork and your curtains and the cushions etc.   There seems to be so many possible combination, that you could almost ask whether every possible combination works.  Is it possible to make colours clash?  I can see my wife holding her hands up.  Of course it is – you do it all the time.

Colour clashing

This diagram accompanies an explanation of Colour clashing.  I admit I’m hopeless.  I look at the diagram and I just don’t get it.  The combinations on the left look just as good to me as the ones on the right.  I would be terrible as a fashion designer.  I would be making faux pas’s all the time.  I think the point is that you wear muted colours with other muted colours and intense colours with other intense colour.  I’ve read several articles that explain colour clashing.  It seems that you can’t mix colours that are dissimilar in intensity or lightness or warmth or hue.  But complementary colours are meant to be opposites!  It’s OK if it is actually the opposite and not just round about close to the opposite.   It seems it’s OK as long as the intensity and lightness are similar.   If they are dissimilar in two or three ways they clash more than just one dissimilarity.  The more different the colours are, the more they clash.

Woodpecker 2b

So is this where I went wrong with my red frame?  The picture I presented was on the left.  I chose a frame with the same red hue as the woodpecker in order to emphasize the red highlights.  Did I choose the wrong intensity (saturation) or lightness?  This is what the judge said.  Do you agree?  I can’t see that the colour was wrong.  I think in retrospect it was just too much.  The contrast of green vegetation next to the red frame draws the eye away from the woodpecker.  You end up looking at the frame.  The thinner red highlight seems to work better. (on the right).  The broad red frame just dominates.

Warmth

What are warm colours? Reds and oranges and browns?  Cool colours, blues and greens?  That seems to be intuitively correct.  Warmth for a fire or a sunset, and cool for water and fern gullies.  I took the two photos below at the same time, just after sunset at Hindmarsh island.  Interestingly you have warm colours looking toward the sun and cool colours looking in the opposite direction.  It is interesting to observe the quality of light.  The colour of objects is altered by the lighting.

Toward Warm

Away Cool

Lifewise landscape painters know that you paint a close object with highly intense colours and high contrast.  However a distant mountain becomes less intense, lower in contrast and cooler (blue) in colour.  This may be important to remember when you are editing landscape photos.  It happens because the light is travelling through air, which absorbs slightly more red than blue.  The same applies to underwater objects, but these changes take place at much shorter distances.  This is what colour theorists mean when they speak of colour warmth.

Interestingly the Kelvin settings for white balance are the other way around.  The Kelvin scale is based on a black piece of metal that is heated to a high temperature.  Like for instance the tungsten filament in a light bulb.  Initially it glows red, then moves through oranges, greens and finally blue at the highest temperatures.  Most cameras have a kelvin setting so that you can adjust for the temperature (colour) of your light source and prevent a colour cast in your image.  This is more important when you are photographing with artificial lighting.  Beware. If you remove the colour cast from the two dusk images above they will begin to look similar, but also bland and uninteresting.

Problems

Colour theory has its limitations.  The premise that you can make every visible colour from a combination of just three pigments is just not correct.  The range of possible colours is excellent for the majority of muted tones, but seems to miss some of the more intense colours.  Painters are often buying tubes of intense pigments, like lapis lazuli  which is made from crushed gem stones.  The traditional pigments just can’t emulate this intense colour.   The range of colours that can be generated from a mixture of pigments is known as it’s gamut.  TV monitors have a gamut, as do computer files like jpeg and RAW.  An interesting problem occurs when you try and translate an image from a jpeg file to the computer monitor and then to the printer.  Each device has a different gamut and there needs to be a translation process by the computer to make them roughly equivalent.  You recall that monitors work on additive colour (Primaries are red green and blue) and printers work on subtractive colour (primaries cyan magenta and yellow).  At the end of the day there are always some tones that don’t work out.

How seriously do you take the theory of colour harmony?  Is there a scientific basis for these choices based on the physics of light and the nature of our colour receptors?  It may all be a system of conventions and traditions.  Every culture and every era of painting seems to have a different way of handling colour.  Perhaps colour harmony is the current fad.

Besides when you are photographing the real world you often find attractive arrangements of colours that should clash.  As one photographer said, let nature be your guide as to what colours work and not your prejudices.  Colour harmony is a useful code if you want to create a certain look.  It is not however prescriptive and absolute.

Photographer as artist

Ok so what has all this to do with photography?  I guess photographers are dealing with colour all the time.  They are selecting compositions based on colour.  It is a misconception that photographers just capture what’s out there.  A photographer is much more creative.  They select the subject, what’s worth photographing, often because of an eye catching colour or mix of colours.  They make creative choices that alter the image.  They are adjusting colour, both during the shoot and afterwards.  Photographers identify and rectifying colour cast and saturation errors.  a little bit of colour theory won’t go astray.

References

Advertisements