Colour blindness

[Walter Bender]

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.

-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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