It’s quite exciting to announce that this week I founded Colour Intelligence with my colleague Dr Kaida Xiao. We have some quite exciting things planned. It’s my second time running a start-up. I formed Colourware Ltd in about 1994 and I only stopped running that company when I became ultra busy at Leeds University in my professorial role and when I was also Head of School of Design. I can’t say any more about what we have planned just now but hopefully I will be able to do that soon.
I received a copy of the book today – A Cultural History of Color in the Modern Age. It is one of a six-book volume published by Bloomsbury. In this one I have a chapter co-authored with Qianqian Pan entitled Technology and Trade. In short, we look at the key technological developments in the 20th century and their effect on culture and commerce. The developments we focus on the growth of the synthetic dye industry, colour imaging technology and colour measurement. You can probably get a copy of my chapter through my ResearchGate page.
You’ll be green with envy if you miss this podcast all about the colour green. Malachite was one of the earliest green pigments and a substantial source was the Great Orme in North Wales (the largest prehistoric mine in the world). Green is also the most dangerous of colours. Scheele’s Green may even have killed Napoleon. The team also discuss the association of green with the devil and with Ireland. The use of colour in movies is also discussed and the use of green in The Wizard of Oz is of particular interest. And did you know that the Statue of Liberty was not always green? You do now. But listen to the podcast for the full story.
Imagine you have a standard (std) and a batch (btx) and you have the CIELAB values of each. How can you analyse these numbers, in particular, the differences? This post explains how to do it.
Let’s start with a real example.
Now what can we say about these two samples. Well, we can calculate the colour difference. If we want to calculate the CIELAB colour difference we can simply calculate the differences in each of the three dimensions, square them, add them and take the square root. Thus DL* = 2, Da* = 10, and Db* = 6. So the CIELAB colour difference is sqrt(4 + 100 + 36) = sqrt(140) = 11.8. This is quite large. Of course, we might prefer to use some other measure of colour difference such as CMC or CIEDE2000. But let’s stick with CIELAB.
The next thing is to look at the individual differences. Since a* is redness we might conclude that the btx is redder than the std (the btx has an a* of 36 whereas for the standard it is only 26). And since b* is yellowness we might conclude that the btx is yellower than the std (the btx has a b* of 9 whereas for the standard it is only 3). However, it is really confusing to look at the data this way. Perceptually, we might be interested in whether there is a chroma difference (is the batch weaker or stronger?) and whether there is a hue difference. Let’s plot these samples in the a*-b* plane of CIELAB.
As you can see, the btx has a larger a* value and a larger b* value than the std. However, we cannot deduce anything about hue or hue differences just by looking at a* or b* on their own. Hue is an angular term in CIELAB space.
As you can see from the above figure, the hue of the standard is 6.6 degrees and the hue of the btx is 14.0 degrees. The CIE method to calculate hue descriptors is to move radially from one sample to another and note which axes we cross. So if we start of with the btx we move clockwise towards the std; we keep going and we cross the red axis and then (if we keep going) we cross the blue axis. So we would conclude that the std is redder (bluer) than the btx. According to CIE guidelines, one of these descriptors makes sense and the other doesn’t.
In this case, I would say that the std is bluer than the btx. In hue terms it doesn’t really make sense to say that the std is redder than the btx when they look quite red anyway. And we would say that the btx is yellower (greener) than the std.
In terms of chroma we calculate the distance from the centre for each of the colours. As you can see from the diagrams, the batch is much further out from the centre than the std.
So, in conclusion, we would say that the btx is lighter, stronger and yellower than the std. The std is darker, weaker and bluer than the btx.
The point of this is to highlight that we cannot make decisions about hue and chroma by looking at just a* and b*. We need to look at both a* and b*. Better than trying to do this is to calculate the polar coordinates, hue and chroma. These are generally more helpful than the cartesian coordinates, a* and b*. In my experience, people have a reluctance to think in terms of polar coordinates and I think this is because they have much greater experience at school with cartesian coordinates. Everyone spends their schooldays looking at certesian plots of x vs. y don’t they? But getting to grips with polar coordinates in colour science will really pay off in the long run.
Notice that just because the batch has a larger a* value than the std, this does not make the batch redder. In fact, as can be seen from the first diagram, it is the std that is closer to the a* (red) axis than the btx, despite having a smaller a* value.
The Over The Rainbow team discuss the colour yellow. Yellow Ochre was one of the earliest pigments used by mankind. Orpiment was also widely used in antiquity despite it being based on arsenic and being poisonous. Yellow has also long been an important colour culturally. The Greeks – starting from Empedocles – believed that the world considered of four elements; each of the elements was associated with a colour. Yellow (or a yellow-green colour) was associated with earth; white with air, black with water and red with fire. This tetradic thinking about 4 special colours continued until the 14th or 15th Century; the idea of three special colours is a relatively recent idea. Yellow is probably the least favourite colour and invokes quite different reactions in different people. It is, perhaps, the marmite of colours.
A number of studies have concluded that wearing the colour red make us seem more attractive to other people. However, perhaps surprisingly, this is still an effect that is unclear. Although many studies have reported the effect, others have not found it.
Today I was reading a paper by Lehmann, Elliot and Calin-Jageman who conducted a meta-analysis of published work on this topic in 2018. They analysed a large number of studies to try to come to a definitive conclusion. Overall they found a small but statistically significant effect when men were rating women. The effect was much smaller for women rating men.
Interestingly, the authors could not agree on the conclusions and presented two concluding remarks in the paper. The first and third author concluded that the effect of red on attraction was small, potentially nonexistent. However, the second author concluded that there was a small but reliable effect for both men rating women and women rating men.
This reminds me a little of the work on the effect of colour on blood pressure and heart rate where, again, the literature show contrasting results. In this area I have concluded that there might be an effect but that, if there is, it is probably very small. Measuring very small effects can be difficult because of the problem of needing large sample sizes.
I have been providing free information about colour on the internet since … well, almost since the internet existed! My posts here on colourchat have received over 300,000 views from more than 200,000 people. But before I ran this blog I ran something called an FAQ. FAQs were on the internet long before blogs and my colour physics FAQ was available for free for decades, providing free information about colour measurement to anyone who was interested. I have also contributed to TheConversation and my post there the effect of colour on our bodies and minds is the 7th most read article on TheConversation by anyone at the University of Leeds with about 170,000 reads. I am passionate about colour education and I am part of the colour literacy project.
Recently I had the idea to generate even better content that can educate about colour and to this end I started a patreon page. For some of this content I am charging a couple of dollars per month for access. But the idea is to generate some funds to allow the highest quality colour education material to be developed. That’s my dream anyway. If you would like to support me doing this – and also see the material that is being developed – please think about supporting me at the patreon website.
Whatever happens I will continue to keep this Colourchat resource free and will post here as often as I can.
What I love about colour is the fact that there is always something new to learn. Today I learned that the experiment with two prisms (often attributed to Newton) where he split white light with one prism and recombined it with a second (inverted) prism is not possible. There is a fantastic youtube video about this that shows that you need a lens between the two prisms to make this work.
https://www.youtube.com/watch?v=uucYGK_Ymp0
Our current consumption of textiles is not sustainable. Perhaps one solution is better design of clothes to allow easier disassembly which could avoid discarded garments ending up in landfill. According to The Australasian Circular Textile Association 90% of textile waste ends up in landfill which is a shocking statistic. Or perhaps there will be a societal change leading to less emphasis on fast fashion. These are issues that we are exploring at the University of Leeds in our Future Fashion Factory. The Future Fashion Factory is a £5.4 million R&D partnership (led by the University of Leeds but including Huddersfield University and Royal College for Art) exploring and developing new digital and advanced textile technologies to boost the design of high-value creative products. The idea of leasing clothes rather than buying them is also gaining traction. Celebrities have long leased evening wear for red-carpet events. But could leasing become more mainstream?
Maybe the future of fashion is virtual. Perhaps in the future (in the near future actually) we will be able to change our clothes as easily as we change our backgrounds when taking part in video calls. Fashion is important and fulfils a desire that people have to express themselves. But perhaps people will increasingly use virtual environments to express themselves. Fortnite has already hosted several fashion shows and fashion is already an essential component of the hugely successful online game. For our children – the future consumers of this world – buying a virtual garment is as natural as buying a physical garment (and possibly more rewarding). The world of digital fashion was recently discussed in an interesting article in The Guardian by their fashion editor Hannah Marriott.
Our regular team on the Over The Rainbow colour podcast discussed these issues with Caroline Hemingray who leads the MA Fashion Marketing at the University of Leeds. You can listen to the podcast here – https://swestland.podbean.com/
For our sixth episode of our colour podcast we chatted about colour in fashion covering colour forecasting and the future of fashion. We brought in a guest, Caroline Hemingray, who leads the MA in Fashion Marketing at the University of Leeds. It’s mainly for fun – and as an educational resource – but I hope you find it interesting. You can see the podcast here.