See Wyszecki & Stiles, Color Science (2nd ed.), 1982, Table 1 (5.14.2) p. 464
The lines shown above are called confusion lines and converge at a point which is called the copunctal point. For the three different types of color vision deficiency there are three different copunctal points.
For the two types of red-green color blindness (protanopia and deuteranopia) the main problem area of colors is really in the axis between red and green. And on this side of the color space, the confusion lines are quite the same for both types. This is why they are called red-green color vision deficiency. But on the left side of the diagram you can see that they are quite different confusion lines which show the problem colors.
If you would like to learn more about color matching and confusion lines you might like to read the article Color Matching and Color Discrimination by Joel Pokorny, a very well known researcher in the field of color vision deficiency.
As you can see from the above diagrams, the whole spectrum of colors is some way reduced for colorblind people. It is definitely not only red and green (protanopia/deuteranopia) or blue and yellow (tritanopia) which can not be distinguished.
The RGB Anomaloscope can be used to check if you are suffering from red-green color blindness or not. Unfortunately it is not possible to differentiate between the different forms of red-green color…
If you are designing graphics for a web page you have to keep in mind to make them also accessible to colorblind persons.
With Photoshop CS4 Adobe introduces soft proofing for color blindness, a great support just for this task.
The new soft proofing filters for color vision deficiency were developed in corporation with the Japanese Color Universal Design, a user-oriented design system, which has been developed in consideration of people with various types of color vision, to allow information to be accurately conveyed to as many individuals as possible.
Adobe Photoshop CS4 supports the following two color blindness filters, which combine the two most common forms of color vision deficiency:
To determine whether your document is CUD-compliant or not, step through the following three simple steps:
Convert the document to RGB color mode, which provides the most accurate soft proofs for color blindness.
To simultaneously view the original document and a soft proof, choose Window > Arrange > New Window (optional).
Choose View > Proof Setup > Color Blindness, and then choose either Protanopia-type or Deuteranopia-type.
To comply with CUD, you have to check your document in both views.
If you are a graphic/web designer, don’t forget to check your graphics on accessibility for colorblind users. Photoshop CS4 is one of the tool which can help you to fulfill this task—the color blindness simulator Coblis another (online) one. You might find some other helpful tools on my list of 15 Tools If You Are (Not) Colorblind.
The question arises now, can such colored contacts really help you if you are colorblind?
Possible view through colored glasses. Photo taken by Malingering
The following discussion refers to a product called ChromaGen, most probably the best known colored contacts aiming to help colorblind people.
The ChramaGen: A practitioner report is the most often cited report about visual aids for colorblind people. Unfortunately this source seems to be very optimistic and more like some surreptitious advertising.
It is well known, that colored contacts can only alter the perceived colors but can not enhance the spectrum. For example Dr. Natalie P. Hartenbaum states very clearly that lenses don’t correct color blindness contrary to some of the vendors, which make it look like as they could cure color blindness with their products.
Colored contact one eye only
Unfortunately I can not tell you anything about my personal impressions as I have never tried such lenses. But I would like to cite some others who did try colored contacts in hope to find something against their color vision deficiency under certain circumstances or even in everyday life.
Faborito says the following about his ChromaGen lenses (Link):
My life has changed in a way a have no words to describe. Last year i saw red for the first time in my life. Is amazing!!!! You have no idea what is like to see a coke can or a tomato in full brilliant red. It’s spectacular. I used them every day, and for photography are great.
Tabascokid is also sharing his story about the Chromagen lenses (Link):
[…] The thing that is not explained in the brochures is that despite you suddenly having a broader range of visible colours, depth perception and contrast, it doesn’t help in actually recognising the colours. When I attempted to edit skin tones and subtle casts, I was still just as much in the dark. The primary colour looked lovely and punchy but I never really had issues with these anyway. Tones and hues were as confusing as ever. My brain still couldn’t get the differences.
With ChromaGen only one tinted lens is worn, this provides colour contrast but I found it distracting as I was unable to coordinate the contrasting visual data. Although I passed the Ishihara Colour Test with this system, I was still unable to name colours. The ColorView system changed the colour spectrum but at the expense of darkening the visual spectrum overall. This system was more akin to wearing sunglasses than anything else as I still was unable to identify colours confidently and still failed the colour test.
Azmole tried the two systems ChromaGen and ColorView (Link)
I did have some improvement when testing them with the Ishihara test. The opthamologist with Colorview had me go outside in daylight to use the lenses and many reds that I normally could not see came into view. I did not purchase the lenses because I was more interested in passing a color vision test and felt even with the lenses I would fail.
Now judge yourself if you wont to give colored visual aids a try to improve your color vision. But you have to know, that not one product can cure color blindness but only alter your color perception.
The following list of on- and offline tools for colorblind persons was put together by JNvB, the founder and owner of www.kleurenblindheid.nl.
This is an overview of available software and websites which either help and assist you if you are suffering from color blindness (Visolve, Daltap, eyePilot™) or tools that can show you how the world looks like for colorblind persons. Next to that, programs are indicated that can recognize color and can show the name and/or code (e.g. RGB).
Daltap has several features combined of which the flashing feature is the most useful. By flashing, it shows where a picked color is on your screen. Next to that, it can give the name of the color at the tip of mouse and it can also zoom in the area that is near the mouse.
The features of Daltap:
Naming feature: show the name of the color (basic and detailed)
Flashing feature: chosen color flashes on the screen
Mini zoom feature: enlarges the area around the mouse
Several filters that allows better identification of colors by graying out all colors except the one chosen or by flashing a picked color. It can also make a color turn black by clicking on the name and it can show the name of color. On top of that, it can change the hue of colors, increasing the contrast between colors.
The filters of eyePilot™:
Gray filter: all colors gray but the picked color
Flashing filter: a chosen color flashes
Name filter: shows the name of the color the mouse points at
Hue filter: adjusts the saturation of colors
Platforms:
Windows NT, 2000 and XP
Mac OS v10.2 and higher
Download: eyePilot™ Fully functional trail version for 30 days. Thereafter an activation code is needed for which you have to pay $34.00.
ColorBlindExt by Onkar Rukar, Gaurav Savkar, and Tushar Pagar
ColorBlindExt
This Firefox add-on offers the possibility to change websites, text and figures such that it is better readable for the colorblind. This can be done while browsing or via a menu with the following filters:
Red filter (for protanopia and protanomaly)
Green filter (for deuteranopia and deuteranomaly)
Blue filter (for tritanopia and tritanomaly)
Monochromacy
Platform:
FireFox 2.0 or higher with Java Runtime Environment 1.5 or Java Advanced Imaging Run Time 1.1.3 or higher.
ColorDoctor not only simulates website display, it is also possible to simulate real-time display of for example moving images such as Flash by selecting the “Transparent” mode. It is possible to show the display content through four different conversion filters:
Grayscale
Protanopia
Deuteranopia
Tritanopia
The simulation result can be stored in various file formats, including BMP, JPEG, PNG, TIFF, and GIF.
Platform:
Windows XP and Vista with Windows .NET Framework 1.1 or higher
Coblis was designed to help non colorblind people to understand how an image looks like if you have a certain type of color vision deficiency.
You can either try the different types of color blindness on the given sample picture or upload your own images and see how they look if you would be colorblind.
The following types of color blindness are supported by Coblis:
The online service of Vischeck offers two types of simulation:
Vischeck: shows how pictures look for colorblind people
Daltonize: corrects images if you are colorblind
Vischeck itself can simulate the three main types of color blindness either using an image or by running it directly on a webpage:
Protanopia
Deuteranopia
Tritanopia
Daltonize makes it possible to adjust the ratio of red/green & blue/yellow and brightness of colors of images making them more readable for a colorblind person.
Next to the website, Vischeck offers a plug-in to do the simulations offline with the help of Adobe Photoshop or ImageJ (see Vischeck downloads):
Enlarges the area around the tip of the mouse and tells which color it points to in several different color systems like HEX, RGB, and CMYK.
Next to that, it is possible to make some image capturing or use the value switchable mode, which allows you to choose between normal, grayscale and websafe colors.
Enlarges the area around the tip of the mouse one to four times and tells which color it points to in several different color systems like RGB, decimal, HSV and HLS.
Additionally it gives the name of the color the mouse points to, which is very handy for colorblind users. And on top of that it can even pronounce the color names.
Platform:
Windows 95, 98, Me, NT, 2000, XP, and Vista
Download: WhatColor Fully functional trail version. Thereafter an activation code is needed for which you have to pay $8.00.
By giving in a color as a RGB, HSB, or hexadecimale colorsystem value, Color Name & Hue associates a color name and the corresponding hue out of more than 1600 colors.
Color names can also be found by placing the circle on one of the main colors followed by moving around the slider to find the hue of the color of interest.
You can either select a color by its name, enter a hexadecimal color value or select a color on a color selector wheel. Name that color will find the closest match out of a list of more than 1500 colors and name it.
Thanks very much to JNvB from www.kleurenblindheid.nl for this comprehensive list of tools for colorblind and not colorblind people. If you know of any more please add them in the comments section.
Did you ever wanted to quickly make a color vision test with one of your friends? Put a few euro coins into your pocket and you will always have a simple color blindness test handy and ready to use.
Euro Coins Color Blindness Test — (left) normal vision, (center) deuteranope simulation, (right) protanope simulation
P. J. Pardo, A. L. Pérez and M. I. Suero, three researchers from the University of Extremadura, Spain, found this simple test while looking for an uncomplicated possibility to test for color vision deficiency. The discovered that there are two different classes of coins:
1, 2, 5 cent coins made of copper-covered steel with a reddish tone.
10, 20, 50 cent coins made of Nordic gold with a yellowish tone.
Measuring the exact colors and calculating the coordinates in the CIE color space showed, that the two different colors are arranged on the deutan confusion line. This means that green-blind people wont be able to distinguish the colors and also red-blind people will have significant problems. So they found a simple possibility to test for red-green color blindness
So this are the facts. And now, how can you perform a color vision deficiency test based on this findings?
Gather 5 coins each from lower and upper values. Use coins from different countries, as they have different back sides.
Mix them and show the coins with the value side facing down to your friend.
Ask your friend to sort all the coins based on their colors.
See how your friend performs on the task.
Explain the facts why this is a valid red-green color blindness test.
Any person with normal color vision should be able to sort them quickly and of course correct. Red-green colorblind people will have more or less problems to sort them and often try to sort them based on brightness. If you try this test on several persons (including colorblind people) you will recognize the difference.
Happy testing! — Check the color vision abilities of your friends and your family with this simple color blindness test. It would be great to hear some of your experiences. If you like, share them in the comments.
Many people think that only men can be colorblind. As we can learn from genetics, this is not true. There are a lot more men colorblind, but also women can suffer from a color vision deficiency.
Here’s a question for experts: according to a vision test in a magazine she did recently, my mother has a slight red-green weakness, which, however, is hardly noticeable in daily life. Is this also colour blindness, although that is really rare in women, and it’s nothing compared to her father’s colour blindness, which was pretty severe? Or can it be due to her being a carrier?
On a first glance it looks like we can give a quick and short answer on this. But thinking about it, makes it a bit more complicated.
First of all, yes women can be colorblind and even if it is a very weak form of it you call it color vision deficiency (a wording which reflects much better the fact that colorblind people can also see colors). And it doesn’t matter if it is rare or not.
Sex chromosome X encodes color vision. XY = man
XX = woman.
Now let’s have a closer look at this case. We have a colorblind man which means he has a defective X chromosome which pairs with a Y. The Y chromosomes have no coding of color vision and therefore have no important role here. His daughter will inherit this defective X and another X from her mother. We have now to possibilities:
The mothers X is also defective concerning color vision.
The daughter inherited an X encoding perfect color vision.
In the first case the daughter definitely shows some form of color blindness which she inherited from both of her parents. It is said that the weaker form either from her father or from her mother would control her color vision.
X-linked recessive carrier mother
According to genetics the daughter shouldn’t be colorblind in the second case. But it is known from different cases that this isn’t always so easy to tell. Up to now it is not fully understood how those two X chromosomes affect the color vision system. It could be very well that both of them play their part in the setup of the color receptors. In this case the strong color blindness encoded on her fathers X chromosome could also affect the color vision to a certain degree.
Putting this together means, that the daughter can show characteristics of color vision deficiency in the first and the second case. Only a detailed genetic analysis could tell us more details about it.
Did you ever wonder how it looks like to be colorblind? It is not easy at all to describe color blindness in words. But it is much easier to show it on an image, if you have the right tool.
Coblis is based on Michael’s color matrix from ColorJack. Basically the tool manipulates the colors of an image in such a way, that the result is the same image as seen by a particular type of colorblind people.
Ever tried to make your own Ishihara plates test? Alon has the answer for all of us who are not that inventive or at least not good with computer programs.
