Re: Color Blindness and TWing

Subject: Re: Color Blindness and TWing
From: Geoff Lane <geoff -at- gjctech -dot- co -dot- uk>
To: TECHWR-L <techwr-l -at- lists -dot- techwr-l -dot- com>
Date: Wed, 12 Apr 2006 21:52:24 +0100

On Wednesday, April 12, 2006, David Loveless wrote;

> So, my questions are these:

> 1. How aware are you of color blindness?
Enough to understand that very few people are colour-blind (i.e. see
no colour at all) but approximately one in eight males have abnormal
colour vision and that significantly fewer women than men are
affected. I also understand that the main cause is genetic, carried on
the X chromosome and is recessive, which explains why women carry
colour vision abnormalities but are less frequently affected.

Many people who have a colour vision abnormality go through life
without ever knowing it. Many in this group might be affected and not
know it. If you don't know whether you are and are interested, search
the 'net for "Ishihara test" - there are lots on-line.

> 2. How much do you understand about color blindness (causes,
> misconceptions, results)?
The biggest misconception I understand is the one about what is colour
blindness. Many people use the term "colour blindness" to refer to any
form of abnormal colour vision. True colour blindness (monochromatic
vision) is extremely rare. Single-colour blindness (complete lack of
one "colour" - protanopia, deuteranopia, and tritanopia) is rare. More
common is reduction of one "colour" from either some receptors
responding to an abnormal frequency range or having lack of
sensitivity (protanomaly, deuteranomaly, tritanomaly).

> 3. How much of an affect and what affects do you believe color
> blindness has on your audience.
Significant if interface colours are badly chosen. For example, one
classic mistake is red on black (or black on red), which is difficult
or impossible to read for approximately one in eight males! Colour
intensity is different for those who have abnormal colour vision. For
example, red is the dullest colour on the pallet for someone with a
strong protanomaly, which makes red lights harder to spot. So, the use
of red to indicate danger probably wasn't selected by someone with a
colour deficiency!

> 4. What steps do you take to limit the problems caused by color blindness?
a. Ensure that no essential information is conveyed by colour alone.
b. Check that all graphics etc. still work when reduced to greyscale.
c. Do not use colours that differ only in red, green, or blue. For
example, don't use blue and purple that are the same colour when
you remove the red from the purple.

> 5. (This one is just for my own kicks and giggles) Are you or a
> technical communicator you know color blind?
FWIW, I have moderate protanomaly.




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Color Blindness and TWing: From: David Loveless

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