Colour blindness

[david at lang.hm]

On Mon, 14 Jul 2008, Walter Bender wrote:

> Tthe classic example of misconstruing value contrast and chromatic
> contrast was when the Human Factors journal decided to switch from
> black-on-white to yellow-on-white for their cover. The switch only
> lasted one issue, as I recall.
>
> We (humans) process spectral information through two distinct
> pathways: chromatic and achromatic. These interacting factors can be
> adjusted to suit the considerations of legibility and emphasis.
> Sustained legibility of large bodies of text is accomplished by a
> combination of colors whose achromatic contrast is large and whose
> chromatic energy is of low to moderate level. The rule of thumb is a
> minimum of two Munsell value steps between foreground and background
> colors. One surprising result is additional contrast makes little
> difference in reading tests. That said, since ambient-lighting
> conditions vary, you are advised to add additional contrast where you
> can.

for the XO you should also remember that there is the monochrome mode for 
the display. when the user switches to it (and/or the ambiant light level 
gets too high) the colors disappear and all that's left is the contrast.

David Lang

> -walter
>
> On Mon, Jul 14, 2008 at 3:13 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
>>
>>> In case it helps, I am quite colorblind (I mix up anything that CAN be
>>> mixed up...) and I haven't had any problems with the keyboard.
>>
>> That's because the original subject of this thread is misleading.
>>
>> The problem is not color, it's reduced contrast.  Any background color will
>> do the same thing.  A lighter green would better,
>>
>> I haven't found a good web page that explains this crisply.  (If anybody
>> does, please let me/us know.)
>>
>> The Readability Guidelines at the bottom of this rant cover it:
>>  http://www.useit.com/alertbox/20020819.html
>> But they assume you know what's going on rather than explaining things.
>>
>> Which reminds me of one of my pet gripes about modern computer aided layout
>> software: they encourage idiots to put text on pictures.  Even Scientific
>> American screwed that one up many many years ago, and they had a reputation
>> for good graphics and such.
>>
>> The same problem happens when web pages use a background color that reduces
>> the contrast.  This is frequently obvious when the background is a picture.
>>
>>
>> Interesting timing.  I was at my doctor's office last Fri, getting a tetanus
>> booster shot.  They gave me a sheet of fine print to read.  It was black ink
>> on red paper.  I could read it, but I think I would have noticed that it was
>> slightly hard to read even without this discussion.
>>
>>
>> PS for vision geeks:
>>  Swordfish have 100 watt heaters behind their eyes.
>>  That's because eyes/brains work better when they are warmer.
>>  http://www.bioedonline.org/picks/news.cfm?art=1511
>>  http://www.soest.hawaii.edu/pfrp/newsletters/Apr-June2005.pdf
>>
>>
>> --
>> These are my opinions, not necessarily my employer's.  I hate spam.
>>
>>
>>
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