Saturday, September 28, 2013

Vision - Color Blindness and Color Perception

Yesterday I posted about color and that led to some interesting discussions and wonderful feedback. It also got me thinking about senses and perception. Vision is different between species. Most people already know that dogs perceive color differently than humans do, and also that some people have color blindness.

Can you see the numbers/letters in each square?

Protanamoly, also called "red weakness" is present in 1 of 100 males which is a huge number. In protanamoly, red, orange, yellow and yellow-green shift towards the the green hue and get pale. When looking at violet, a person with protanomoly will see blue.

The red tones of the grapes on the left are reduced or eliminated
in protanamoly, leaving the grapes looking blue.

A second type of color blindness is termed deuteranamoly or "green weakness". This is present in 5 out of 100 males, much more prevalent than protanomoly. Again, the small differences between red, orange, yellow and green blend but in the deuteranomoly individual although the colors blend to the green hue, they don't get pale but instead, they retain their brightness.

What a difference!  The changes between panels two and three are
not just color but also hue/intensity. The colorful world is a
world of shades of grey for a large proportion of the male population.

The majority of people with protanomoly or deuteranamoly will go through life without any difficulty and sometimes without even realizing that they are "color blind". But men who suffer from dichromasy are seriously affected and it affects their daily life in all aspects. There are two types of dichromasy - protanopia and deuteranopia.

Protanopia sees the color wheel like this.

Protanopia reduces the brightness of red, orange and yellow so much that they pull into the greys and blacks and reds become almost invisible. Coping mechanisms can be developed, but the lack of color differentiation will impact daily life.

Deuteranopia blends colors on the wheel into larger
groupings but keeps the brightness of the reds,
oranges and yellows. 

Deuteranopia keeps the brightness but again, eliminates the differences between red, orange, yellow and green. The colors have names, but look exactly the same to a person affected by deuteranopia. I suspect it would be rather like looking through a patterned shower door trying to discover the occluded figure below.

By Silent Reaper

Finally there is synthesia, but I love the aspects of synthesia so I'll tackle this in a separate post at another time.

I see examples of color and people's ability to discern color every day in my shop. My business is color - blending and contrast, complementary and shaded. I love color and my customers do too. But it's not unusual for customers to choose a dark blue for a purple, demonstrating the inability to see the red in the purple beads. It is said that Van Gogh saw more than 15 different shades of yellow. I never found that surprising because I have fine color sense, but after studying color perception in more detail, I now understand why that is considered so remarkable.

Here's a quick comparison of what people with red-green color blindness
actually see when confronted with a color test. The standard vision
disks are on the left. Can you see all the embedded numerals?

Are you interested in testing yourself or others for colorblindness and color perception? Here's a great link for you with several different tests that you can administer yourself.

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