Download my colour physics FAQ e-book for the Kindle here.
Also available as a physical book from Amazon.
The answers to these and many other related questions about colour physics are each provided in a short and easy-to-understand form. Will delight and entertain colour professionals and curious members of the public.
Pink is one of my favourite colours. Generally, however, if you ask people what their favourite colour is, the most frequent response is blue irrespective of gender, age or culture. Adults, that is. Because most young girls prefer pink. There is a huge commercial machine that pushes girls towards pink and boys towards blue. I support the Pink Stinks campaign which I blogged about in 2009, but I fear its chances of success are slender.
In my 2009 I linked to a BBC article that noted that pink for girls and blue for boys was not always the case. People cite the Ladies’ Home Journal from 1918 saying:
There has been a great diversity of opinion on the subject, but the generally accepted rule is pink for the boy and blue for the girl. The reason is that pink being a more decided and stronger colour is more suitable for the boy, while blue, which is more delicate and dainty, is prettier for the girl.
For some reason I always thought that it was the association of blue with the British Navy in the first world war that started the association of blue with boys. But today I read an article that suggests that the association did not start until the 1950s!! Apparently in 1927, Time magazine surveyed 10 major departments stores across the country about how each store associated pink and blue with boys and girls. The results showed that most children dressed in gender-neutral clothing and typically wore white because it was easy to bleach and keep clean. It wasn’t until the 1950s that pink became a female colour according to Estelle Caswell. Read all of what Estelle had to say here.
The first synthetic pigment – Egyptian Blue – was made by the Egyptians around 4500 years ago. A technique developed by scientists at the British Museum has allowed them to discover traces of Egyptian blue on ancient objects that no longer have their original paint finishes intact. Before the Egyptians learned how to make a synthetic blue pigment from sand and copper the main blue pigment was obtained from the mineral lapis lazuli, first found in Afghanistan about 4500 BC. Extracting blue from lapis lazuli was extremely expensive.
Blue remained an expensive pigment however and came to symbolise truth, peace, virtue and authority in fine art. Images of Mary usually showed her wearing a blue robe. Blue was used for symbolic reasons. Cheaper blue pigments became widely available in the modern era of synthetic pigments.
Further details can be found here.
This looks interesting. Node is a way to add sensors to your iOS device. It allows you to measure all sorts of things, including colour if you have the node+chroma combination. The node costs about £100 and the additional sensors cost about £50 each. I am not sure how much the chroma sensor costs.
You can find further details here – http://variableinc.com/chroma-contact/
Electronic displays can vary in their characteristics. Although almost all are based on RGB, in fact the RGB primaries in the display can vary greatly from one manufacturer to another. Colour management is the process of making adjustments to an image so that colour fidelity will be preserved. In conventional displays – desktops and laptops – the way this is achieved is through ICC colour profiles. Colour profiles store information about the colours on a particular device that are produced by RGB values on that device. So to make a display profile you normally need to display some colours on the screen and measure the CIE XYZ values of those colours; you then have the RGB values you used and the XYZ values that resulted. The profiling software can use these corresponding RGB and XYZ values to build a colour profile so that the colour management engine knows how to adjust the RGB values of an image so that the colours are displayed properly. Building a profile often requires specialist colour measurement equipment – though this can often be quite inexpensive now. If you are using your desktop or laptop display and you have never built a profile then you are probably using the default profile that was provided when your display was shipped. The default profile will ensure some level of colour fidelity but particular settings (such as the colour temperature or the gamma) may not be adequately accounted for. If you want accurate colour then you should learn about colour profiling.
It all sounds simple except for the fact that ICC colour profiles are not supported by iOS or Android operating systems on mobile devices. I find this really surprising but that’s how it is for now. Maybe it will be different in the future.
This means that ensuring colour fidelity on a smartphone or tablet is not so straight forward. So what can you do?
Well, there are two commercial solutions to this problem that I am aware of. They are X-rite’s ColorTrue and Datacolor’s SpyderGallery. ColorTrue and SpyderGallery are apps that will use a colour profile and provide good colour fidelity. These are great solutions. Perhaps the only drawback is that the colour correction only applies to images that are viewed from within the app. Having said that, they allow your standard photo album photos to be accessed – but the correction would not apply, for example, to images viewed using your web browser. This is why a proper system implemented at the level of the operating system would be better, in my opinion.
There are two alternatives. The first would be to implement your own colour correction and modify the images offline before sending them to the device. This would not suit everyone – the average consumer who just wanted to look at their photos for example. But it is what I typically do here in the lab if I want to display some accurate colour images on a tablet. But if you were a company and you wanted to display images of some products for example – it might be a reasonable approach. It has the advantage that the colour correction will work when viewed in any app on the device because the colour correction has been applied at the image level rather than the app level. But it does mean you need to do this separately for each device and keep track of which images are paired to each device. This is ok if you have one or a small number of devices but maybe not so good if you have hundreds of devices.
The second alternative would be to build your own app. If you want to do things with your images that you cannot do in ColorTrue or SpyderGallery or if you have lots of devices and you can’t be bothered to manually convert the images for each device, then you could install your own app that implements a colour profile and then does whatever else you want it to do.
Yesterday I spoke an an event to launch Samsung’s latest curved screen displays. The technology is really gorgeous and everyone who attended was wanting one of the new displays after seeing them.
I am convinced that curved screens will become ever more popular in the future because not only do they look good but they offer serious advantages for users who undertake intensive tasks – the sort of tasks that need a large desktop display rather than a mobile device. When it comes to desktop displays it is really quite simple – bigger is better.
Many people – and I am one of them – are what is known as ‘double screeners’. I have two screens attached to my desktop and my operating system is spread seamlessly across them because I wanted more screen space to work in. I recently carried out a survey – you can find more details here – which showed that 38% of British office workers are already using two or more screens attached to their desktop computers.
Of course, in an ideal world one very large screen would be better than two smaller screens. But there is a problem with most flat-screen technology which is that the LED/LCD pixels emit light straight out but emit a lot less light at an angle to the screen. This means that you look at a large flat screen the light reaching your eye from the edges of the screen is a lot less. Not only that but, because you are looking at the screen at an angle, text and other fine details can be distorted at the edge. Curved displays get around this problem and I am hoping to replace my two flat screens soon with a single Samsung curved display.
With a curved display the distance from the eye to the screen is the same across the whole display and the angle of view is also constant. Not only does this solve the colour and acuity problems I just mentioned but it means that users need to need fewer eye and neck movements. Given that many of us spending longer using a display than we do actually sleeping this could have a big effect on user well-being.
Our survey also showed that about 60% of office workers think it is important that the office technology they use looks good. This can help to motivate them and help them to feel good about themselves. The new Samsung curved displays certainly will satisfy these people.
The cameras never lies. Or does it? Recently I had to take a photo for a medical case and before submitting it I had to sign to say that the photo had not been modified. I did this – but it was ridiculous of course. Many people have this idea that the cameras faithfully captures what the scene looks like and that, unless we intentionally manipulate the images (in photoshop, for example), then we have captured the truth. Nothing could be further from the truth – as the recent image of #TheDress showed.
The top photo above was taken and released by NASA in 1976 and shows a Martian landscape. The sky is blue. However, at the time, Carl Sagan said “Despite the impression on these images, the sky is not blue…The sky is in fact pink.”
You see the original image had not been colour corrected. Colour correction is a process that takes place on most cameras these days without the user being aware of it but in 1976 was not automatic. The process can compensate for the spectral sensitivities of the camera sensors (which may differ from one camera to another) or for the colour of the light source. The second picture (above) shows the colour-corrected image. Some people are now arguing, however, that the amount of colour correction applied by NASA is wrong and that the sky should not be as red as it appears on the second photograph. For the full story including some other nice images of Mars see here.
A student was asking me about use of colour in a design (that showed text on a background) today and one of the things I said to her was “Get it right in black and white”. Prof Lindsay MacDonald taught me this. The idea is to make sure there is contrast in lightness and that you are not relying on a contrast in hue for people to read the text. So, for example, if you must put red text on a green background – I don’t advise this particularly, but if you do – then make sure it is a dark green and a light red or a light green and a dark red.
In the above two images, one is easier to read than the other. In both cases the hue of the red and green are the same. But in one case there is a large lightness difference and in the other there is not. if you were to print these out in black and white, one would be more readable than the other. That is what, “Get it right in black and white means.” It’s sensible if for no other reason than it increases the chance that someone who is colour blind (most are red-green colour blind) would be able to read it. Of course, maybe red and green would be not great colours to use in the first place – but that is a longer story.
I have come across a really lovely interactive website that helps with this. It is called colorable. It allows you to enter two colours (in hex format) – or use slider bars to control hue, lightness and saturation – and then it gives you a WCAG contrast ratio and even a pass/fail decision about whether you meet the minimum guidelines. Please try it – it’s great fun.
Really super article by Ana Swanson in the Washington Post about colour vision and how it works. As she explains, it is not really correct to think of the long wavelength visible light as being red. It is better, as Newton knew of course, to say that the long-wavelength light has the ability to cause the sensation of redness in us. She gives a nice visual example of how the spectrum looks to a dog, something (by coincidence) that I was only talking about in a lecture last week. As she says:
Is what I see as “blue” really the same thing as what you see as “blue”? Or have we both learned the same name for something that looks different to each of us?
Her article is really worth reading.
There is just one thing I take issue with. It may be ‘nit picking’. But she says “A green leaf, for example, reflects green wavelengths of light and absorbs everything else.”
My image, at the top of this post, shows the reflectance of a typical yellow object. At each wavelength the reflectance is between 0 and 100 per cent. But notice that it is not zero at any wavelength in the range shown (400-700nm). That means that the object reflects light at every wavelength. And it is not 100 at any wavelength meaning that it also absorbs to some extent at every wavelength. It’s just it absorbs more at the shorter wavelengths than at the longer wavelengths and it reflects more at the longer wavelengths than at the shorter ones. But notice one other remarkable thing – the yellow object reflects more light at 700nm (a wavelength we would normally associate with red) than it does at 580nm (a wavelength we might normally associate with yellow).
Yes, the reflected light does look yellow. But, the notion that a “A yellows object reflects yellow wavelengths of light” is misleading. It suggests that the yellow object only reflects, for example, the wavelengths in the spectrum we would normally think of as yellow (around 580nm) and absorbs the rest. This is just not how things are.
I just saw an interesting article by Kim Lachance Shandrow about how the colour of your office can affect productivity. The article refers to a paper (2007) in Color Research and Application (CRA) by Nancy Kwallek entitled Work week productivity, visual complexity, and individual environmental sensitivity in three offices of different color interiors. The paper suggests that the influences of interior colours on worker productivity were dependent upon individuals’ stimulus screening ability and time of exposure to the interior colours. CRA is a top quality academic journal that is peer reviewed and so I am respectful of the findings.
However, in Kim’s online article there is a lot of stuff that I am highly sceptical about. For example, she writes that “Red … increases the heart rate and blood flow upon sight.” Is this true? Is there really any evidence for this. I have two PhD students working in this area right now and I am far from sure that colour does affect heart rate and, if it does, the effects are probably tiny. And yet we can read statements like this all over the internet as if it is a fact beyond doubt. Other things she says that I take with a pinch of salt is that “green does not cause eye fatigue” and that “yellow triggers innovation.” Don’t get me wrong – I am very interested in how colour can be used to affect us emotionally, psychologically and behaviourally; it’s just there is a danger that if some things are said often enough (such as red increases your blood pressure or heart rate) then people start believing them even though there may be little evidence.
That said, you might find the infographic fun and it is well done. See the original and full article here.