eyes change colour?

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reindeer

I didn’t realise how sophisticated reindeers are. It turns out they have two layers of fur to help them keep warm, are able to shrink the pads on their hooves to give then better grip, and can detect ultraviolet light which enables them too see in very dim light. And it also turns out that their eyes can change colour in winter so that their vision is more sensitive. Reindeers, like cats, have a reflective layer behind the retina (which is the inside of the eye ball where all the light-sensitive cells are) that helps them to see in dim light. This is why, if you see a cat at night, you might see the eyes shining; you are seeing light being reflected back at you from the cat’s tapetum lucidum (which is the technical term for the layer behind the retina). The light that shines back in most animals with this layer is golden but in reindeer it apparently shifts to blue in the winter. The shift to blue allows more light to be scattered and improves the vision of the animal.

The full paper can be read in the Proceedings of the Royal Society.

good reasons to use colour

art, culture, design, , , , , ,

I just came across this nice article – http://understandinggraphics.com/design/10-reasons-to-use-color/ – entitled 10 reasons to use color.

The article lists 10 good reasons to use colour in design. Number 10 is using colour for metaphor and taking advantage of the associations that are inherent in phrases such as feeling blue or green with envy. There is no doubt about the meaning in the image below; that the woman is filled with envy.

color-for-metaphor

AIC2014

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logobig-full
As some of you may know, I was General Chair of AIC2013 this year. We had a great time in Newcastle and spent a week with over 600 delegates talking about colour. But time moves on and we are approaching 2014. I would therefore like to draw your attention to the next AIC meeting which is in Mexico in October 2014. The theme is colour and culture and the venue – Oaxaca – is stunning. I hope to see you there.

For further details visit http://www.aic2014.org/index_en.html

Where is colour mixing?

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Imagine that we have three projection lamps at the back of a hall – one has a red filter and so produces a beam of red light, and the other two use filters to produce green and blue beams. We project these onto a white screen and get three circles of light (one, red, one green and one blue). We then move the angles of the projectors so that the circles of light overlap. We get something that looks rather like this:

ColourMixing

Where the red and green light overlap we get yellow. We get magenta and cyan for the other two binary mixtures. So,

red + green = yellow

red + blue = magenta

green + blue = cyan

This is called additive colour mixing as I am sure you know. And if we mix all three primaries we can achieve white (or other neutral colours). The primaries could be single wavelengths of light – so we could use a primary at, say, 700 nm (for the red) and one at 450 nm (blue) and one at 530 nm (green). So green light (530 nm) and red light (700 nm) additively mix together and generate yellow. When this happens what is being mixed and where does this mixing take place? Take a few moments to consider this before reading on.

Notice I said that they additively mix to generate yellow – I specifically avoided saying that they mix to generate yellow light. When I sat down with a couple of students last week and asked then what they though they said that the red and green light mixed together to create yellow light and when I pressed them, they went further to say that the yellow light was at about 575 nm.

visible-a

If we measure the part of the screen that is yellow we would see that we have some light at 700 nm and some at 530 nm. The wavelengths are not mixed; they don’t mix together to generate some third wavelength of light such as 575 nm. So no physical mixing takes place other than – I suppose one could argue – that the red and green lights are mixed in the sense that they are spatially coincident. But that’s not really mixing, for me, and certainly doesn’t even begin to explain why we have the sensation of yellow when we look at these wavelengths together. It also makes me think that additive colour mixing, if it can be said to occur anywhere in particular, occurs in the eye. And I do mean eye, not brain.

Welcome to my blog

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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. I am also offering more detailed information about colour on my patreon page so take a look there if that might be of interest. 

The Colourchat blog is now sponsored by Colour Intelligence

 

is there such a thing as visible light?

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I would argue that there is no such thing as visible light – or at least that the term visible light is a meaningless one.

Light is part of the electromagnetic spectrum which is describes electromagnetic radiation by its wavelength. An electromagnetic wave has both electric and magnetic field components. What is really very interesting is that depending upon the wavelength of the field the electromagnetic radiation has very different properties and we give it a different name.

electromagnetic-spectrum

When the wavelength is very long, the radiation is radio waves or micro waves. When the wavelength is very short, the radiation is x-rays or gamma rays. There is a narrow range of wavelengths (from about 360 nm to about 780 nm – a nm is 0.000000001 of a metre) to which our eyes are sensitive. Because we can literally see this radiation we call it light. I still find it amazing that light, x-rays, radio waves, and microwaves are all essentially the same thing (electromagnetic radiation) with just a change in the wavelength!! However, my point for today is that light is radiation that is visible – to talk about visible light would be bizarre since by its very definition light is visible. Technically, visible light is a pleonasm; pleonasm is a word derived from the Greek word “pleon” meaning excessive. Other examples of pleonasms – easily confused with oxymora – include the phrases end result and invited guests.

swatchmate

design, news, professional, technology, , , , ,

Very interested in this new colour-measurement device called the swatchmate cube.

swatchcube-color-matcher-designboom03

The new device is launched by Swatchmate on November 13th. That;s two day’s time from now. It captures the colour and displays it on your smartphone. Does it provide any numerical data such as CIELAB? I don’t know. How much is it? I don’t know. I guess we’ll find out at the launch!!

Cadbury lose purple case

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cadbury

I have written a few times about various legal cases that are on-going to settle disputes about colour ownerships. For example, about 18 months ago I wrote about trademarking colour and the dispute between Cadbury and its competitors over the use of the colour purple (specifically Pantone 2685C) on chocolate packaging and advertising. In that blog I noted that Cadbury had lost a case in the USA against Darrell Lea but had been granted protection in the UK despite protests from Nestlé. The law is a complex matter.

However, today, in the BBC I read that Nestlé has won a court battle with Cadbury, over Cadbury’s attempt to trademark the purple colour of its Dairy Milk bars. This is a successful appeal by Nestlé to the earlier ruling. The Court of Appeal said that Cadbury’s trademark application lacked “the required clarity, precision, self-containment, durability and objectivity to qualify for registration”.

“We are disappointed by this latest decision but it’s important to point out that it does not affect our long held right to protect our distinctive colour purple from others seeking to pass off their products as Cadbury chocolate,” said a Cadbury spokesman. Watch this space!!

Colour survey

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personal care products-1
I am currently carrying out some research using an on-line questionnaire about colour choices by consumers in product design. It would really help me a lot if you would take the survey. It only takes about 1 minute to complete. The link is http://questionpro.com/t/AKSnxZP9ij. Please feel free to share this link.

In a few weeks when the survey is completed you can come back to this page and you can see more details about what we were doing, why we were doing it, and what we found.

Steve