Monthly Archives: October 2009

two cultures?

This week I was honoured to be the invited speaker at the 5th National Conference of the Italian Colour Group. I decided to address the meeting about two of my research projects that to some extent attempt to bridge the gap between art and science.

In 1959 CP Snow – a Cambridge University academic – delivered a famous lecture entitled The Two Cultures that led to heated and widespread debate. Snow argued that the lack of communication between the sciences and the humanities was a problem that inhibited solution to the world’s major problems.

I believe that Snow’s argument is still valid today. Interestingly I bought The Times to read on the plane to Palermo – where the colour conference was being hosted – and to my surprise that very day’s edition had a substantial article about The Two Cultures –

The Times writes that Snow said “There is something wrong with a civilisation, he said, where knowledge is so compartmentalised that people can count as highly educated and yet be wholly ignorant of huge swaths of what other highly educated people know. How could scientists not read Shakespeare? How could literary people never have heard of the second law of thermodynamics?

In terms of colour, I believe there was more cross-over between the sciences and the humanities in the 18th and 19th centuries than there is now. I am not convinced that the problem that Snow articulated has gone away. Perhaps the divergence between the two fields is an inevitable result of specialisation? Possibly, but I don’t think so. I think there is room (indeed, a requirement) for specialists. However, we also need to find a way for people working in colour to in the arts and humanities and in the sciences to communicate more effectively to each other. Because, we have much to learn from each other.

In my experience some scientists do not want to communicate outside of their narrow discipline. Others, would like to but seem unable to do so without recourse to specialist language (e.g. mathematics). In the arts, if anything the willingness to communicate “across the gap” is even less. 

One organisation that has worked hard for many decades to encourage debate across the science-art divide is the AIC (the International Color Association”. You can find their website here –

I know from the nice stats that wordpress provide that a lot of people read my blog. But not many people leave any comments 🙁

It would be rather wonderful if – having read this – you left your view at the bottom. Is there a gap? Is it a good or a bad thing? How can we bridge it?

ps. I am not holding my breath waiting for the responses 🙂

subtractive mixing – why not RGB?

In a previous post I spoke about the difference between additive and subtractive mixing and why the additive primaries are red, green and blue or RGB for short –

The chromaticity diagram – see – has a very useful property. If you plot the chromaticities of two lights, then the straight line that joins the two points on the chromaticity diagram show you the additive mixtures that can be obtained by mixing together the two lights. If we take three lights, then the additive mixtures that can be obtained are defined by the triangle that is formed if the chromaticities are the vertices of the triangle. Ok – that’s a bit of a mouthful so let’s have a practical example. The triangle in the diagram below shows the gamut that can be achieved when we have three additive primaries that are positioned at the corners of the triangle.


 From this diagram it should become obvious why the additive primaries are RGB. Say, we chose, two reds and a cyan as the three additive primaries – well, the triangle would be tiny. In other words, the gamut would not be very big. The biggest triangle in the chromaticity is one whose vertices are formed by a red, a green and a blue. WhichRGB will give the biggest triangle? I don’t know – it’s been something that has been puzzling me for the last few days and I’ll come back to this in a later post. But certainly any RGB triangle is pretty large as long as the red, green and blue primaries chosen are reasonably saturated.

So what happens if we choose RGB as the subtractive primaries? Subtractive colour mixing describes how inks and paints mix together to form colours. The first thing to point out is that subtractive colour mixing is not additive and linear – you remember I said that when you mix two lights together the colour mixtures all fall on the straight line that joins the  two points in the chromaticity diagram that represent the two lights? Well, this is only true for additive colour mixing. So to work out the gamut for subtractive systems is not an easy thing to do. However, if you do select the three subtractive primaries as RGB you’ll get a gamut that looks something like this:


Notice that the gamut is concave. Mixing red and green lights produces a nice yellow. You can test this by going into your colour-picker in software such as Photoshop or Powerpoint and setting the RGB values to be 255:255:0. You’ll get a nice yellow. But mixing red and green paints – it will give you a similar hue to yellow but you’ll get something quite desaurated; most likely you’ll get a brown. So using RGB as the subtractive primaries would not be a very good thing at all.

It turns out that additive and subtractive colour mixing are very related. The best subtractive primaries are the ones that control the amount of red, green and blue light reflected. A yellow dye applied to textiles, for example, mainly absorbs short wavelengths in the blue section of the spectrum, allowing the other wavelengths to be reflected by the textile. The “other wavelengths” that are reflected give yellow. But the important point is that the yellow dye absorbs blue. Similarly, a magenta dye absorbs green and a cyan dye absorbs red. This leads to the idea of the optimal subtractive primaries being those that are cyan, magenta and yellow or CMY. This leads to a gamut somewhat like this:


The biggest gamut for subtractive mixing is obtained by using CMY as the primaries. But weren’t you taught at school that the subtractive primaries are red, blue and yellow? Almost certainly you were – and this is because it is accepted dogma at most art colleges and in many art and design textbooks. But it is quite easy to show that the optimal primaries – those giving the largest gamut – are CMY not RBY. If you were building a colour-reproduction system using only three colours such as a printer you would come to the conclusion – as companies such as HP, Xerox, and Epson have done – that you get the largest colour range with CMY. So why has it become commonplace for artists to refer to red, yellow and blue as the primaries? Could it be a colour naming and language issue – that they really mean cyan when they say blue and it’s just a naming error. Possible, but not likely in my opinion.  I think it is more likely that most artists are not overly concerned that RYB gives a smaller gamut than CMY because they rarely restrict themselves to three primaries. An artist would typically use 6 or more primaries. For example, they might use two blues (one that is reddish and one that is greenish), two reds (one that is yellowish and one that is bluish) and two yellows (one that is greenish and one that is reddish) in order to easily be able to mix a wide range of colours. The (mis-)identification of RYB as the subtractive primaries has much to do with colour wheels. I like to keep each of these blog posts reasonably concise – if I start writing about the problems of colour wheels now I will be writing for another 2 hours. And it’s nearly midnight now so colour wheels will need to wait for another day!

silver still the most popular car colour

Pittsburgh-based PPG Industries Inc. said silver has been the number one colour for nine straight years, accounting for 25 per cent of vehicle paint choices in the U.S., 35 per cent in Europe and 34 per cent in the Asia-Pacific region.

In the U.S., silver rose from 20 per cent of the market a year ago. White finished second at 18 per cent and black was third with 16 per cent. Red was a distant fourth at 12 per cent. See

However, it would be interesting to see a more detailed analysis by car type and model. I used to have a Mazda MX5. It was bright red. Although the dark grey MX5 looks nice, for the MX5 you really have to have red in my opinion. It’s iconic.

Having said that, I just searched for MX5 on Google images. It produced, on page 1, 10 silver cars, 5 red cars, and 2 blue cars. So the power of the iconic little red sports car could be weakening and silver could be reigning supreme.

My longing – like that of many others of my age – for a little red sports car probably goes back to The Graduate and Benjamin Braddock’s red Alfa Spider (see picture below).