Welcome to my blog

I am passionate about sharing my knowledge about colour to anyone who is prepared to listen. I work as a professor of colour science at the University of Leeds, in the School of Design, but I have held academic posts in departments of Chemistry, Physics, Neuroscience, and Engineering. Sounds like a mixed bag, but my interest was colour chemistry, colour physics, colour neuroscience, colour engineering and colour design. You see I have come to believe that colour is the perfect meta-discipline and that to understand colour you need to be able to understand (but not necessarily be an expert in) different fields of knowledge.

One way to use this blog is to just browse through it and dip in here or there. However, another way is to click on one of the categories (that interest you) such as culture, design, fun, and technology and see posts in that area. You can find the categories on the right-hand side of the page if you scroll down.

You can also comment on the blogs. I really like this, even if you disagree with me. Someone once said to me if you put ten colour physicists in a room and ask them a question (presumably about colour physics) you’ll get 10 different answers. Well, I guess not all of you reading this are colour physicists. Given our different interests and backgrounds, and given the complexity of colour, it’s not surprising that we will disagree from time to time. And that is rather the fun part.

If you have a technical question you’d love me to answer you can click on Ask Me and post it there. You can also email me at s.westland@leeds.ac.uk

The Wizard of Oz

This week I had to mark about 50 essays that had been submitted for the Colour: Art and Science module I teach at the University of Leeds. One essay looks rather like another after the first 10 or so. So it was a delight to discover that one student had decided to focus on a movie – The Wizard of Oz – and demonstrate her understanding of colour by analysing this classic movie.

It reminded me of a story my mother told me. When she went to see the Wizard of Oz in the cinema (she would have been about 8 at the time) she had never seen a colour movie before. She was so much looking forward to this new-fangled and exciting technology. It’s hard to imagine how exciting that would have been – if every movie you had ever seen had been in black and white!!

Well, imagine her disappointment when the movie started and the movie was black and white after all. For those who don’t know, the movie starts off in black and white (in the Kansas scenes) and only turns coloured when Dorothy is whisked off by the tornado and dropped off in the land of Oz. It must have been a wonderful moment when the screen just turned full colour!!

Indigo – a colour of the rainbow?

From time to time I come across web pages and groups of people who get irrate about indigo being in the rainbow. There is even a facebook group called “Get Indigo out of the rainbow”. It was Newton who suggested that the rainbow contains seven colours: red, orange, yellow, green, blue, indigo and violet. It has been suggested that, at the time, Newton was trying make some anology with the musical scale and the octave (with its seven intervals) and hence was keen to identify seven colours in the rainbow or visible spectrum. Many modern commentators claim that only six distinct colours can be observed in the rainbow.

Interestingly, the facebook group referred to above would like to eject indigo from the spectrum on the basis that it is not a primary or secondary colour but rather a tertiary colour. The group shows the following colour wheel:

colour wheel

In this so-called painters’ wheel the primary colours are red, yellow and blue and the secondary colours are orange, green and violet. It is argued that since six of the colours in the rainbow are primary or secondary colours in the colour wheel and indigo is not, then indigo has no right to be there. This is wrong on so many levels it is hard to know where to start.

The first thing I would have to say is that this argument seems to ignore the difference between additive and subtractive mixing. Additive mixing – http://colourware.wordpress.com/2009/07/13/additive-colour-mixing/ - describes how light is mixed and the additive primaries are red, green and blue. The additive secondaries are cyan, magenta and yellow. Orange is not in sight – and yet surely if we are to make an argument for inclusion in the spectrum based on primaries (and/or secondaries) then it is the additive system that we should be using since the spectrum is emitted light.  

The optimal subtractive system primaries are cyan, magenta and yellow (with the secondaries being red, green and blue) though the artists’ colour wheel (which is like the painters’ wheel above) has red, blue and yellow as the primaries. 

In my opinion there is nothing special about the colours that we see in the spectrum. Indeed, orange is clearly a mixture of red and yellow and does not seem to me to be a particularly pure colour. I just do not think that arguments to exclude indigo from the spectrum based upon colour wheels or primary colours is valid. That said, I have already mentioned that many people believe that indigo cannot be seen in the spectrum as a separate colour; but this is a phenomenological observation not dogma. I am one of those who believe that indigo and violet cannot be distinguished in the spectrum and therefore I agree with the aims of the facebook group even if I do not agree with their arguments.

The really interesting question is why we see six (or even seven) distinct colour bands in the spectrum when the wavelengths of the spectrum vary smoothly and continuously? I have postulated some possible reasons for this in an earlier post – http://colourware.wordpress.com/2009/07/20/colour-names-affect-consumer-buying/ - but it is far from a complete and convincing explanation. It may explain why we see distinct colours in the rainbow, but why six and why those six in particular. Comments on this would be very very welcome.

Do women use more colour names than men?

I just came across this funny cartoon about the difference between men and women in terms of colour names.

doghouse_color_wheel_altered

But on the same page I found the results from an actual colour survey where over five million colours were named across 222,500 user sessions. One aspect of the results is shown below:

doghouse_analysis

It does seem that there is some evidence that women use more colour names than men – though generally there was agreement between how the names were used. For further details see the original article.

Press coverage of #TheDress

Whatever anyone thinks about the colour of dress and the attention it is received there is one undeniable fact – this story had received huge attention from the public and from the media. That in itself is probably more interesting than the debate itself.

The Daily Mirror story covered the angle that we are all right whatever we see because colour exists only in our heads. According to Dr Paul Knox, a reader from the University of Liverpool’s department of Eye and Vision Science, “Colour isn’t something that exists in the world. Different wavelengths of light exist and can be observed but colour is something we make up inside our heads.”

ITV also took the view that the explanation is that colour doesn’t exist. I broadly agree with this view, but the interesting thing is that that doesn’t explain why there was so much disagreement about the colour in this particular case whilst normally we barely notice any disagreement. If it is simply that colour doesn’t exist then why do we ever agree about colour at all?

On the other hand, in the Guardian an article by Bevil Conway considers cognitive processes in our colour vision and visual strategies that may vary from one person to the next. Of course, Bevil Conway is a super scientist and I agree with almost everything he says. Certainly, cognitive strategies could have something to do with this phenomenon. However, when he says that “By accident or design, the dress is a carefully created composition of orange and blue that confounds our visual systems,” I have to disagree. If you look at a properly taken photograph of the dress or the dress itself in real life what you see is shown below:

dress_original

The dress is not a carefully crafted composition of orange and blue – the dress is blue and black. However, Bevil is probably talking about the image that was circulated not the one shown above. To understand this phenomenon you need to understand colour imaging and the fact that colour images are sometimes not faithful reproductions. One of the reasons why this story has run and run is that there is no simple answer, no 10-second soundbite that can put the story to bed. It is a complicated phenomenon.

Extraordinary facts relating to the vision of colours

In 1794 John Dalton presented a lecture to the Manchester Literary and Philosophical Society about colour vision. The first two sentences are shown below:

It has been observed, that our ideas of colours, sounds, tastes, etc. excited by the same object may be very different in themselves, without our being aware of it; and that we may nevertheless converse intelligibly concerning such objects, as if we were certain the impressions made by them on our minds were exactly similar. All, indeed, that is required for this purpose, is, that the same object should uniformly make the same impression on each mind; and that objects that appear different to one should be equally so to others.

It is interesting to reread this sentence again in the light of the recent controversy about the blue and black dress.

Dalton

colour and language

One of the things that #TheDress controversy has highlighted is that colour is not as fixed as the majority of people believe. We tend to think that objects have a single colour and that we all see that colour the same way. However, in the image below you can see two central grey patches that are physically identical but probably look different in colour to you. My experience is that the majority of people would explain this as the two grey patches being the same colour but looking different in colour because of the background. An illusion.

90

I don’t agree with this way of thinking however. The colours we see when we look at something do depend upon the other colours around it but this is not a a special case. It’s not unusual, as Tom Jones would say. It’s how colour works. If it is an illusion then it’s happening all of the time, almost whenever you are looking at colour. So what is the real colour of something? Is it even sensible talk about an object having a single fixed real colour?

There is a body of research emerging that suggests that the language that we use influences how we see things. Jules Davidoff, a Professor at Goldsmiths University, went to Namibia where he conducted an experiment with the Himba tribe, who speak a language that has no word for blue or distinction between blue and green. When shown a circle with 11 green squares and one blue, they couldn’t pick out which one was different from the others. But the Himba have more words for types of green than we do in English. When looking at a circle of green squares with only one slightly different shade, they could immediately spot the different one, even when the difference was so small that we would find it very difficult to see the odd one out. See below for an example.

davidoff

In the image above – a screenshot from one of Davidoff’s experiments – the Himba tribe can easily see that the green patch at about 1 o’clock is different from the others.

In fact, some people even think that in ancient times we could not see blue at all because we had no word for it. In the Odyssey, Homer famously describes the “wine-dark sea.” But why “wine-dark” and not deep blue or green? It turns out that most ancient languages (including Greek, Chinese, Japanese and Hebrew) did not have a word for blue. Does this mean that they didn’t see blue? Is blue a relatively modern phenomenon? There is a thought-provoking article about this by Kevin Loria at Business Insider. Read more here.

final word on the dress

Yesterday, I posted about The Dress that people see as either blue and black or white and gold. Following several radio and telephone interviews I wanted to have a final attempt to explain what is happening with the dress. It is quite an extraordinary phenomenon – yesterday the dress looked blue and black to me but my PhD student (looking at the same dress on the same screen) said it looked whitish and gold. When I came home last night and looked at the photo on my mac book, the same image that had looked decidedly blue and black to me before now looked whitish and gold. So what is happening?

The first thing is that it is nothing to do with the dress. The problem is with the photo of the dress. I believe that anyone looking at the dress in real life would certainly call it blue and black and also anyone looking at the manufacturer’s photo of the dress would also call it blue and black.

The second thing is that there is more than one phenomenon going on. The reasons why my PhD student and I saw different colours in my office may be a little different from the reasons why I saw it one colour on my pc in my office during the day and another colour during the evening on my mac. So, although people might like a simple answer and a soundbite, in my opinion the explanation is necessarily a little detailed. But I will try to avoid too much technical jargon below.

The camera does lie
I think many people believe that when they take a photograph and put in on the internet and people look at, what people are seeing is a faithful rendition of the original scene. People take this for granted, I believe, without giving it much thought. Unfortunately, this is not guaranteed. There are many reasons why the colour someone might look at in an image might not be the same one that was in the original scene. Different cameras capture colour in different ways depending upon the type of camera, the settings on the camera, and the light under which the image is taken, to name just three factors. In The Dress image, the image looks over-exposed and the colours are washed out. The black is quite pale and has a colour tint and the blue is very washed out and insipid. Hopefully you can see where this is going already.

Different displays show colour differently
You can put the same image on a PC, a mac, a smart phone and a tablet and look at it. The colours will probably not be identical. Reds will probably be red and blues will be blue. But the colours are likely to be not exactly the same on the different devices. If you are looking at your screen from an angle, the colours may change radically. Also, if you are looking at your screen in bright sunlight the colours may look more washed out – though some smart phones and tablets try to ‘intelligently’ correct for this which might make the problem better or worse. The fact that I saw the colours differently in my office than at home could be due to differences in the devices I was using or could be due to the lightening environment, The lighting in my office is quite different to that in my home, for example.

People see colour differently – a little bit
About 1 in 12 men are colour blind. Very few women are afflicted. But even for the rest of us – so-called normal observers – there is variability in our colour vision. One factor for this could be that there are known to be differences in our eyes from person to person. This effect could be small but may be a factor in this story. More important is probably the fact that if sit in a dark room for a while and get used to the dark our vision will be different to it would be if we were outside in bright sunshine. This so-called ‘adaption’ is one way our visual systems deal effectively with such a wide range of brightness from dark rooms to brightly illuminated outdoor scenes. Someone coming into a room from outside (where the sun and sky are very bright) might very well see different colours on the screen than some who had been in the room for a much longer period. These adaption factors are well known in science.

People don’t always agree on colour names
There are at least 3 million different colours in the world. How many colour names can you think of that we could broadly agree on? Words like, blue, black, red etc. There are others like beige and taupe where we might agree less well. But include these and how many do you have? 30? 50? 100? And these names have to cover 3 million colours!! So each name is a category that covers quite a large range of colours. Last year I published a paper where we gradually moved a colour from yellow to green and asked people to tell us when the colour went from yellow to green. Not surprisingly, the point at which people told us the name changed varied from person to person. So there are some colours that some people will call yellow and other people will call green. Correspondingly, just because two people are calling a colour by different names does not necessarily mean that they are seeing it as a different colour.

My final explanation
Variabilities in displays, viewing conditions, observers and colour-naming boundaries can cause disagreement in how to name colours. Normally, this would not shift a black to a gold or a blue to a white. However, in this case, the image that has caused the controversy is not a faithful reproduction of the original. Because of the way the image was taken the black has shifted considerably away from the centre of the category that we would call black. And likewise for the blue. In my office today I would still call it black. But it was not a strong convincing black. It was a little pale and had a bit of colour in it. To be honest, I could understand why someone else might call it gold. The colour was on the boundary between black and gold and now differences between people could cause it to be classified as one colour or the other. When I came home, the colours had shifted for me. I don’t think my colour naming boundaries had shifted. Rather, I think this was to do with the lighting I was viewing the colour in, or the screen (a mac rather than my pc) or the angle I was viewing my screen at. Any or all of these factors could have shifted the colour so that it passed from the category I call black to the one that I would call gold.

Maybe the surprising thing is that these controversies do not happen more. Colour imaging scientists have been phenomenally successful in delivering colour imaging devices that satisfy consumers. Part of this work is done at the University of Leeds where I work but there are other places around the world who make great contributions including RIT in Rochester USA. And then there are some super bright scientists in places like Samsung, Apple, HP and LG who have worked hard to understand the complexities of colour perception and colour communication to the extent that people barely even think about these issues. However, there is more work to be done. Colour is still a major factor in people being dissatisfied when they buy something over the internet. When the product arrives it is sometimes not the colour they expected it to be. And colour fidelity is still not good enough for many medical applications. If you want to get involved in colour science please contact me. My email is s.westland@leeds.ac.uk and you can also find me @stephenwestland

#TheDress

I was asked to comment on the radio today about a dress which is topping the trends of social media in the USA in particular today.

2622C22600000578-0-image-a-32_1425001827044

The dress has sparked controversy because different people say that it is different colours. There is a group who say it is blue and black and another group who say that it is white and gold. What do you think?

I will give my explanation but it is not simple so …

Now, about 1 in 12 of all men in the world are colour blind. But if we consider the rest of the population you may be surprised to know that there is variability in our colour vision. This is mainly due to the colour receptors in our eyes. Put simply, some people have more red receptors and some people have more green receptors, for example. So we know that we don’t all see colour in the same way.

There is a second complexity and that is just because we use different names for a colour doesn’t mean we see it differently. This most often happens with brownish colours where some people will refer to it as more of a green and others will be adamant that it is definitely a brown. So words – colour names in particular – are not always very precise. We can see at least 3 million colours in the world and how many names do we have? A few hundred at least.

There is a third complexity which is that people think the camera never lies – that is, that they take an image of something using their phone and put it on the internet and everyone is seeing a faithful reproduction of the thing they took a picture of. Sadly, the camera does lie. Variability in the light that is used to capture the image, the settings on your display (whether you have a warm white or a cool white, for example) and how bright the light is in the room when you look at your screen – these can all dramatically affect the colour. Take a look at the picture below:

dress_original

This is the manufacturer’s photo of the dress. Taken professionally, I think most people would see it as blue and black. But the image that is on the internet is very different. I suspect it was taken in a very bright light and the colours are consequently a bit washed out.

So, in summary, the camera does lie. I think the lighting conditions under which the photo was taken were far from ideal and have changed the colours from how they would have appeared if you had been there. However, that is only half the story. Since people looking at the same image on the same screen are disagreeing with the colours. To fully explain what is going on you need to invoke the knowledge that we can sometimes see colours differently (because of variability from one person to the next) and even if we see the colour the same we might give it a different name (because colour names are crude ways to communicate colour).

Of course, fundamental to this is the idea that things are not coloured at all but your brain constructs a colour from the signals it receives in the eye. This allows us, for example, to discount changes in colour that may occur when the light source changes (this is known as colour constancy). We have evolved to discount the effect of light being bluer or yellower, for example, so that we normally see the colours that the object would have in neutral daylight. In the case of the dress image it may be that people are using different processing strategies and discounting the effect of the light source in different ways.

Which all goes to show that colour is complex. But if you have been reading my blog you already know that, don’t you?

guess what – red is sexy

red is sexy
Guess what? Another article that concludes that women wearing red are more likely to attract a mate. Scientist claims women are reflecting their sexual intentions ‘from the beginning’ by wearing bright red clothing. It’s a shocker!!! Who would have thought it!

It must be true because I read it in the Daily Mail.

Colour and Manchester United

van gaal

It’s not often I get to write about two of my favourite things at the same time. So I couldn’t resist remarking on a story today in the Daily Mirror about a colour code that Manchester United manager Louis van Gaal uses to describe different players in his squad. Apparently:

Blue:
“A blue player is intellectual and is always looking for structure and security in his job on the pitch.”

Red:
“A red player is creative, full of power, will want to work and is always focusing on the future.”

Green:
“A green player is very emotional, sensitive for different emotions or a different atmosphere in the squad.”

See the original article for the colours that the newspaper thinks that different players should be be allocated.

It couldn’t get much blacker

black
A few weeks ago I was taking my son to a birthday party and a journalist from The Independent phoned me to ask my opinion on Vantablack. This is the blackest material ever made. Whereas most black materials reflect about 4% of the light (or more) at all wavelengths, this new nano-material has really really low reflectance. It only reflects about 0.035% of the light. I gave a few comments and an article appeared in The Independent which was nice. I used to really like The Independent, back in the days when I read newspapers. The original article by Ian Johnston was very good imho.

However, a few days later the story was all around the world and I was often cited, all based on that one phone interview with Ian. The thing was that it was not even that big news. That is, yes, it is the blackest material ever made, but the truth is it is an incremental improvement in blackness beating the previous blackest material from a few years ago. My name even appeared in the Daily Mail. Most embarrassingly, I was interviewed on an American radio show. The reason I say it was embarrassing was that this new development actually had nothing to do with me and I didn’t want people thinking I was trying to claim credit. So when I agreed to do the radio show I told the researcher that they needed to be clear that this was nothing to do with me. I didn’t invent it. Imagine my surprise when John Hockenberry (that was his name, I believe) asked me, “So Dr Westland, what have you stumbled upon?”. Arghhhhh!!! Luckily, it was not a live interview because it actually got worse. A lot worse. So bad, that I could barely summon up strength to listen to it when it went out the next day. But actually, the editors did a good job and the final cut is not too bad. You can hear it here.

It would be nice to talk about my own work. I work in the area of blackness. One of the things I do is to ask people to rank different black samples in order of least black to most black. This allows me to discover, for example, that women prefer reddish blacks and men prefer bluish blacks. Also, asians prefer reddish blacks and caucasians prefer bluish blacks. I am developing a blackness index; a way to measure a sample and say how black it is or whether one sample is blacker than another. Why? Well, one application is for manufacturers of black ink for printers (which may be made from coloured inks). Different recipes produce different blacks. What if one recipe is chromatically neutral but another recipe is less neural (it has a slight hue) but is darker – which one is blacker?