# Re: Equation for determining color "closeness"

From: Roberto Ellero <rellero@webaccessibile.org>
Date: Sat, 30 Aug 2003 09:55:07 +0200
Message-ID: <002101c36ecc\$3ae51020\$3a29fea9@K6jt1f6N1cl0f>
To: <w3c-wai-gl@w3.org>
```
I found interesting this mensurability of the contrast.

I noticed that the complementary colour (directly opposite to each other in
the colour wheel) combination has the highest contrast.
http://www.webwhirlers.com/colors/combining.asp
"Split complementary is a colour and the analogous colours to its complement
color. Using split complementary colours can give you a design with a high
degree of contrast, yet still not as extreme as a real complementary colour.
It also results in greater harmony than the use of the direct
complementary."
http://www.color-wheel-pro.com/color-schemes.html#split

Maybe this site is useful:
http://www.4colorvision.com/files/colorcontrperf.htm
It's about contrast performance of the human eye.

It is interesting also to notice that even the chromatic contrast
sensitivity functions are subjected to a logarithm:
http://www.4colorvision.com/files/colorcontrperf.htm#equations

Best regards,
Roberto Ellero

----- Original Message -----
From: "Wendy A Chisholm" <wendy@w3.org>
To: <w3c-wai-gl@w3.org>
Sent: Saturday, August 30, 2003 12:38 AM
Subject: Equation for determining color "closeness"

>
> On page 93 in Chapter 4 (Creating Accessible Content) of "Constructing
> Accessible Web Sites" [1], Jim Thatcher writes, "It is clear that good
> contrast occurs when two colors are close to complementary. 'Closeness'
can
> be calculated as if the R G B colors are points in the three-dimensional
space:
> Distance = ( (R1-R2) ^2 + (G1-G2) ^2 + (B1-B2) ^2) ^1/2
> "
>
> [1] http://www.jimthatcher.com/book.htm
>
> --
> wendy a chisholm
> world wide web consortium
> web accessibility initiative
> http://www.w3.org/WAI/
> /--
>
>
```
Received on Saturday, 30 August 2003 03:59:44 UTC

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