This is not yellow

A few people have asked me about this interesting and entertainig youtube clip – This is not yellow.

It’s worth looking at. It makes the point that when you look at colours on the screen (whether it is your computer screen, your TV or your mobile phone) although you see a full range of colours, all that is there is mixtures of red, green and blue light. In principle this is true – in practice it’s a bit more complicated because the screen doe snot emit just three wavelengths. For practical reasons the RGB primaries on a display are more broad band. Nevertheless, the essence of what is being said is true; when you look at yellow on the screen it is not a single wavelength that you would associate with yellow that is being emitted. Hence, the “This is not yellow”.

However, the clip doesn’t go far enough. It suggests that this is a problem with displays and that when you see a real lemon, for example, you are seeing real yellow because the lemon absorbs all the wavelengths of light except yellow (which is reflected). Sadly this is not true either. Let’s look at the reflectance profile of a typical yellow object. I can’t promise it is a lemon but a lemon would be pretty similar.

What this graph shows are the wavelengths of light along the x-axis and, along the y-axis, the per cent of each wavelength that the yellow object reflects. Notice that it does not absorb all wavelengths excecpt the ones that would be seen as yellow in the spectrum (essentially about 580 nm). Rather, the physical yellow object reflects all wavelengths in the spectrum because the reflectance is greater than zero at all wavelengths. The physical yellow object also absorbs all wavelengths in the spectrum to some extent because the reflectance is less that 100% at all wavelengths. Obviously some wavelengths are reflected more than others. But it isn’t even the wavelengths at about 580 nm that are maximally reflected. The yellow object reflects more red wavelengths than it does yellow wavelengths. So why does the lemon look yellow? For the same reasons that the lemon looks yellow on the screen; because the light being reflected activates the cones in the human visual system in a certain way. So I am not knocking this video – rather, I want to say that it makes a good point about displays but that this point also relates to colours in the subtractive world. It raises the issue of what we mean when we say something is yellow either on a screen or in the physical world.

colour and accessibility

Just came a across a superb article by Geri Coady, a designer and illustrator living in Newfoundland (Canada) about the importance of designers taking into account the fact that about 5% of the population in the world are colour blind. Well, it’s mainly men of course ….. but that’s all the more reason to take into account [joking].

Some really excellent advice about how to take colour blindness into account in design work. She talks about problems with the use of colour in London’s iconic underground map (see my blog about colour blindness and maps). She also comments on a game (Faster than Light) that has a colour-blind mode; I mentioned last week that SimCity was doing something similar. About time. It’s so lazy not to take colour blindness into account in the digital environment. There are also some great links to simulators.

chicken colour vision

Most humans are trichromatic; that is, our colour vision is mediated by three types of light receptor in our eyes. These receptors are known as cones and the three types have peak sensitivity in different parts of the colour spectrum. We sometimes refer to these as LMS cones because of their peak sensitivity at long-, medium- and short-wavelengths light.

Some people (men, in the main) are colour blind and this is because they are anomalous trichromats (they have three cones but the spectral sensitivities are less optimal than they should be or they are dichromats (they are missing the L, M or S cone types). But what about other species?

Most mammals are dichromats including dogs and cats. However, many fish and birds have better colour vision than do we humans. I just came across an article that reports that chicknes have five cones compared with our three. The research has been conducted the Washington University School of Medicine in St. Louis (USA). It is suggested that birds often have more cones than we do because they descended directly from dinosaurs and never spent any part of their evolutionary past living in the dark.

what is it like to be colour blind?

Another simulator on the market that shows you what your image or website would look like to someone who is colour blind. This one is from a company called ETRE – for further details see http://www.etre.com/tools/colourblindsimulator/

In the image series below the left image is normal and the ones in the middle and right show protonopia and deuteranopia respectively.

For more on colour blindness see my earlier post.

SimCity for the Colour Blind

A while ago I posted about whether colour blindness was something that designers should take more seriously. After all, about 8% of all the men in the world are colour blind. Of course, this does not mean that they cannot see colour (the term, colour blindness is a bit of a misnomer) but it does mean that they have difficulty discriminating between colours that the rest of us can easily tell apart. In my original post I was referring to the computer game, Call of Duty, and whether the gameplay could be reduced for colour blind players who may have difficulty telling the various colour tags apart that appear on the screen.

So it was quite interesting that I just came across news that the developers of SimCity have added three special colour filters that make adjustments to the colours on screen so that colour blind players can better discriminate. A great idea – but about time!!

new colour blogs

Readers may be interested in a new colour-related blog by the SDC’s Chief Executive Graham Clayton. The SDC – the Society of Dyers and Colourists – is the world’s leading independent educational charity dedicated to advancing the science and technology of colour worldwide. It is a professional, chartered Society and becoming a member gives access to SDC’s professional coloration qualifications. I have been a member since about 1982 and I am a Chartered Colourist and a Fellow of the SDC.

I also recently came across another colour blog called chromatic notes. It’s not clear from the web site who runs this blog but there is a great deal of technical information there.

Race for colour

The films were made by a young British photographer and inventor called Edward Turner, a pioneer who can now lay claim to being the father of moving colour film, well before the pioneers of Technicolor.

The footage will be shown to the public from 13 September at the museum in Bradford. And a BBC documentary, The Race for Colour, will be broadcast on 17 September in the Yorkshire and south-east regions on BBC1. I will feature in the film for a minute or two. Exciting.

For further details see the story in the Guardian.

on-line test for colour blindness

Quite a lot of people are colour blind and have poor colour discrimination. There are tests that can be carried out and these include the Ishihara test (which is a screening test that I certainly remember from School) and the Munsell 100-hue test (where people have to arrange a number of coloured discs in order). These tests need to be performed whilst being viewed in daylight. There are online tests but these are less reliable – partly because the viewing conditions vary such a lot. I recently came across a new online test provide by X-rite. It seems to be based on the 100-hue test (or, at least, something similar) and I can see how it could work, despite being an on-line test). I just had a go. It gave me a score of 34 and suggested that for my age group (and gender) the best score was 0 (perfect colour acuity) and the worst was 99 (low colour acuity). Hmmmmmmmmm. I have a version of the 100-hue test and I can perform it perfectly. My real score should be 0. I have perfect colour discrimination. So, much as I like the X-rite test, I have not changed my opinion that on-line tests like these should be used for fun and should be understood to not provide an accurate assessment of your colour vision. On the other hand, it could just be bitter because I only scored 34.

special females

Our colour vision results from the fact that our eyes contain three types of light-sensitive cells or cones that have different wavelength sensitivity. Some people (called anomalous trichromats) are colour blind and this is usually because one of their cones is mutated and has a different wavelength sensitivity compared with those in so-called normal observers. Colour-blind is a misnomer really because anomalous trichromats can still see colour; they just have less ability to discriminate between colours than normals. Some people are missing one of the cone classes altogether and are referred to as dichromats; they have even poorer colour discrimination but can still see colour. Only monochromats are really colour blind and they are extremely rare.

For a long time I have known that some females have four cones classes (this makes them tetrachromats). Dr Gabriele Jordan, a researcher at the Institute of Neuroscience (Newcastle University) has spent the last 20 years working on human colour vision. She has discovered that tetrachromatic females exist and that although this gives them the potential for colour discrimination much better than normal trichromats in practice most have normal colour discrimination. However, in a recent report she has found a tetrachromat who really does have enhanced colour discrimination. This is really exciting news!

The report in the Daily Mail suggest that a functional tetrachromat could be able to see 99 million more hues than the average person. Personally I am skeptical of this claim even if, as I suspect, it means 99 million more hues than the average person. The number of colours that an average person can see is debatable but I think may be about 10 million (see my previous blog post).

UK goes red, white and blue mad!

This was a picture taken whilst shopping in Tesco today. There are union jack flags everywhere you look at the moment in the UK. The Olympics has not even started yet – the reason there are so many flags already is, of course, the sixtieth anniversary of the Queen taking the throne of the UK. The red, white and blue colours of the union flag – red = Pantone 186 (C), blue = Pantone 280 (C) – derive from a combination of the three flags from England, Scotland and Ireland.

The English flag dates from 1194 when Richard I introduced the cross of St George as the national flag of England.

The Scottish flag was a diagonal white cross on a blue background.

When Queen Elizabeth I died, the scottish king James (King James VI of Scotland) inherited the throne of England and became James I. James I proclaimed himself King of Great Britain and essentially unified England and Scotland. But which flag to use? A new flag was created that was a combination of the previous two and known as the Union flag. A white boarder was added around the red cross because the rules of heraldry demanded that two colours must never touch each other.

The union flag was used at sea from 1606 but became the national flag of Great Britain in 1707 under the reign of Queen Anne. We now had the United Kingdom of Great Britain. In 1801 Ireland became part of the United Kingdom. The Irish flag had been a diagonal red cross on a white background.

The combination of all three flags resulted in the familiar Union Jack.

The name was later changed to United Kingdom of Great Britain and Northern Ireland when the greater part of Ireland left the United Kingdom in 1921.

Why is Wales not represented in the Union Jack? To read why this is please visit here.