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List: kde-accessibility
Subject: Re: [Kde-accessibility] how blue must blue be for blue-on-yellow
From: Gunnar Schmi Dt <gunnar () schmi-dt ! de>
Date: 2008-01-24 14:07:16
Message-ID: 200801241507.24325.gunnar () schmi-dt ! de
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Hello,
On Montag, 21. Januar 2008, Matthew Woehlke wrote:
> [...]
> Ok, so I keep hearing that blue-on-yellow colors are for a11y
> specifically... that being the case, I suppose I'm going to go ahead and
> add that scheme to kdea11y.
I created all three high-contrast themes (black on white, white on black,
and yellow on blue) for KDE 3.x after I read somewhere that they are
necessary. However, I did not really ask for specific reasons at that
time, and the only color scheme where I had input from people with low
vision is the white-on-black color scheme, so I do not know whether the
yellow-on-blue color scheme really meets the needs of those persons that
may need such a color scheme.
> What doesn't entirely make sense to me is what's wrong with
> white-on-black for most cases (rod deficiencies as opposed to cone
> deficiencies, where someone can tell about colors but not lightnesses?).
> Anyway... how important is it that the blue be #0000ff as opposed to
> #0000c0 and there-abouts?
I would guess that people with rod deficiencies are unusual. From my basic
knowlodge about how the eye works I would guess that even these people can
tell the difference between white and black, but they might not be able to
differentiate different shades of gray that easily.
I know, however, that there are people that need a high contrast, mostly
dark color scheme, but for whom white text on a black background is a too
large contrast (they are dazzled by the white and therefore cannot read
what is written). I would expect that the yellow-on-blue color scheme is
needed for these persons as yellow is darker than white (and brighter than
blue) and blue is brighter than black (and darker than yellow).
> Put another way, would the scheme in [1] (that tries to balance being
> blue-on-yellow with "something that won't cause blindness in 'normal'
> people ;-)") be adequate, or do things really, really need to be
> #ffff00-on-#0000ff?
>
> 1: http://img178.imageshack.us/img178/3632/olympusrh8.png
As I have said above, I created the yellow-on-blue color scheme without
feedback from users of it. In fact, it is a modification of an earlier
version of the white-on-black color scheme where white is replaced by
yellow and blue is replaced by black.
If my assumption about possible users of the color scheme is correct, I
would argue that the scheme you suggest is problematic in the way that it
increases the contrast of the yellow-on-blue color scheme by partly
lightening the yellow and partly darkening the blue.
That said, the theme looks much better than my attempt on a yellow-on-blue
color scheme to my non-impairmed eyes (but as I said, it may not be what
the users of a yellow-on-blue color scheme need).
> Matt Blissett [...] noted that the selection could use more contrast
> (actually, there is already more contrast than in the KDE3 version,
> but it's still not very good). What's the safest way to do that; make
> the selection lighter, or everything else darker? Or is it "good enough"
> and changing it is likely to cause problems?
Please keep in mind that persons with low vision need a good contrast
between the text and the background color in order to be able to read.
Differentiating the brightness between two different shades of background
colors can be done with a far smaller difference than reading text.
I hope that my comments are usefull for you,
Gunnar Schmi Dt
--
Co-maintainer of the KDE Accessibility Project
Maintainer of the kdeaccessibility package
http://accessibility.kde.org/
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