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A quick introduction to colorblindness

About 8% of the male population has some form of colorblindness. In this article well

take a look at the basics of how colorblindness works.

Posted on10 Jan, 2012

TypeArticle

Categoriessticky

Theoretics

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To see anything at all we need some tiny little helpers inside our

eyeballs, the so called photoreceptors. There are two different types

of them: rods and cones. Both of them are sitting on the retina at the

back of your eye and pass information on to our brain. The rods are

sensitive to light while the cones pick up color.

Each of the cones is carrying one out one of three different

photopigments red, green and blue and reacts differently on

colored light sources. For each of this three types there exists a

specific color absorption curve with peaks at different points in the

color spectrum.

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Mixing together the information of those three different types of

cones makes up our color vision.

Now, when one type of cones malfunctiones the color this cone

would normally absorb is altered. This changes the color perception,

resulting in a (somewhat) different way of perceiving color. This is

what we call colorblindness.

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Types of colorblindness

The tree types of cones translate into tree main types of

colorblindness:Deuteran (green),Protan (red) and Tritan (blue).

In each of these cases, the affected cones can either be mutated or

defective. A mutated cone causes a slight shift and a defective cone

causes bigger shift in the color perception. This results in a total of

six types possible types of colorblindness.

The Deuteran (green) and Protan (red) inefficiencies are the most

common ones:

Deuteranomaly: malfunctioning green cone (common)

Deuteranopia: missing green cone (rare)

Protanomaly: malfunctioning red cone (rare)

Protanopia: missing red cone (rare)

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Blue-type colorblindness is also possible, but very rare:

Tritanopia: missing blue cone (very rare)

Tritanomaly: malfunctioning blue cone (very rare)

Its a male problem

About 8% to 10% of the male population is colorblind.

Colorblindness is most present in males due to the way genetics

work (see footnotes). Only an estimated 0.5% of the female

population is colorblind. Tritan-type colorblindness is not gender

specific, women and men are equally affected.

Type Prevalence

Deuteranomaly (green) 4.63%

Deuteranopia (green) 1.27%

Protanomaly (red) 1.08%

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Type Prevalence

Protanopia (red) 1.01%

Tritanomaly (blue) 0.02%

Tritanopia (blue) 0.03%

Its not all black and white

There are many people who think the colorblind cant see any color.

But the term is misleading, more than 99% of all colorblind people

can see color.As you can see, people with the two most common types of

colorblindness Deuteran (green) and Protan (red) dont really

suffer a radical change in the way they see color.

However, they do have limited ability to distinguish between reds

and greens (and any other color that has their missing color in it),

especially in shades of a certain color. Something might look green,

but in certain situations it could also look red or blue.

The red and green cones lie quite close to each other in what colors

they perceive (see the graphs above). They intersect at various

points; when the green cones dont work, the red ones still pick up

some green and the other way around.

The greens might not be as green as a non-colorblind person would

perceive it, but its still within the category we would call green.

The Tritant (blue) colorblind have the blue end of the spectrum

missing or altered. There is very little intersection between the other

cones, this explains the big change in color perception.

The following table lists some of the most problematic colors for

each main type of colorblindness:

Type Problematic colors

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Type Problematic colors

Deuteran (green)

Green/red, green/blue, green/gray,

green/brown, blue/purple, orange/red,yellow/orange.

Protan (red)purple/dark blue, orange/green,brown/dark green, red/brown,

green/yellow, gray/purple

Tritan (blue)blue/yellow, violet/yellow-green, red/red-

purple, dark blue/black, yellow/white

In conclusion

All of this might sound very medical and confusing, but the basics

are very simple;

The colorblind have a narrowed color perception.

Green is still green and red stays red most of the

time, but not as vibrant or bright as a non colorblind

would see it. Colors lie closer to each other, especially

shades of colors.

In the next articles Ill explain how these basics of colorblindness

translate into practical difficulties, common frustrations and

(usually) easy solutions.

Footnotes

The two common types of colorblindness (red-green and green-red)

are the types of colorblindness that will be most discussed on this

site. There are various other types of colorblindness with different

perceptions, mutations and causes; they are however quite rare.

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So as not to confuse the message with different clauses or oddities I

wont focus too much on these other rare types in general examples

or articles. However, in the end any given solution or analysis will

also work for these types of colorblindness.

Much of the information above is based on and used with

permission from the most excellentcolblindor.comby Daniel Fluck.

More information on the working of colorblindness can be found in

theColorblind Essentials series.

For more information about the genetics side of colorblindness, take

a look atthis article on colblindor.com

http://www.colblindor.com/http://www.colblindor.com/http://www.colblindor.com/http://www.colblindor.com/2010/02/23/color-blind-essentials/http://www.colblindor.com/2010/02/23/color-blind-essentials/http://www.colblindor.com/2010/02/23/color-blind-essentials/http://www.colblindor.com/2006/03/07/the-biology-behind/http://www.colblindor.com/2006/03/07/the-biology-behind/http://www.colblindor.com/2006/03/07/the-biology-behind/http://www.colblindor.com/2006/03/07/the-biology-behind/http://www.colblindor.com/2010/02/23/color-blind-essentials/http://www.colblindor.com/