Re: Colour contrast algorithm when black is used

OK, I'm fine with that.

I think it's important that we are having this discussion on list so that
we have documentation and a paper trail in response to those who may
criticize our 20 year old algorithm, and may be upset that we don't have an
updated algorithm for 2.1. Here's a summary of what I see:

* The algorithm was a real win for us in WCAG 2.0 because it gave us a
mathematical measurement, rather than WCAG 1.0 which was fuzzy:
         "2.2 Ensure that foreground and background color combinations
provide sufficient contrast when viewed by someone having color deficits or
when viewed on a black and white screen. [Priority 2 for images, Priority 3
for text]."

* There has never been, to our knowledge, another algorithm which has
superseded this one.
* The ugly combinations that pass WCAG that people complain about (i.e.,
black on dark orange) I've never seen as I've done WCAG 2 evaluations over
the last 8 years.
* When a new algorithm becomes available we are certainly open to vetting
it and incorporating it in a future version.


Does that sound right?


Cheers,
David MacDonald



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On Mon, Aug 21, 2017 at 4:25 AM, Alastair Campbell <acampbell@nomensa.com>
wrote:

> Hi David,
>
>
>
> I think we would be in very dangerous territory if we try and patch the
> algorithm without a lot more data.
>
>
>
> Just anecdotally from testing, I’ve seen at least two groups (which
> probably have sub-groups) who’s perception of contrast differs from mine:
> low-vision and older-people.
>
>
>
> Strong colours to my vision were muted or invisible to them, and in
> one-case the other way around. For example, a colleague with red/green
> colour blindness can read dark-blue on black easily where I can barely tell
> there is text there.
>
>
>
> As people (Jared, Amelia I think?) mentioned, there are differences in
> perception due to hue, but unless we’ve got research around the whole
> colour gamut for lots of different ‘vision’ types, I don’t think we should
> try patching the algorithm.
>
>
>
> The advantage of the hue-less algorithm is that it ‘works’ regardless of
> hue perception. Not perfectly, but to some degree that makes an improvement
> in general across groups.
>
>
>
> Cheers,
>
>
>
> -Alastair
>
>
>
>
>
> *From: *David MacDonald
>
>
>
> Could be...
>
>
>
> for a 2.1 we're probably not going to solve it all, unless we're super
> lucky... I'm thinking about a minor tweak from what we know now that would
> have broad appeal and plug significant holes.
>
>
>
> So if there's a simple amendment in a colour space, that would be
> awesome... I'll be interested in Jared's suggestions.
>
>
> Cheers,
> David MacDonald
>
>
>
> *Can**Adapt* *Solutions Inc.*
>
> Tel:  613.235.4902 <(613)%20235-4902>
>
> LinkedIn
> <http://www.linkedin.com/in/davidmacdonald100>
>
> twitter.com/davidmacd
>
> GitHub <https://github.com/DavidMacDonald>
>
> www.Can-Adapt.com <http://www.can-adapt.com/>
>
>
>
> *  Adapting the web to all users*
>
> *            Including those with disabilities*
>
>
>
> If you are not the intended recipient, please review our privacy policy
> <http://www.davidmacd.com/disclaimer.html>
>
>
>
> On Sun, Aug 20, 2017 at 1:10 PM, Patrick H. Lauke <redux@splintered.co.uk>
> wrote:
>
> On 20/08/2017 11:41, David MacDonald wrote:
>
> There recently was a Twitter discussion about colour contrast combinations.
>
> https://twitter.com/davidmacd/status/899215930445754368
>
> There seems to be consensus from stakeholders that when black #000000 is
> contrasted against some colours, the 4.5 threshold is met even when it's
> hard to see. I've noticed this for years, and it seems others have too, but
> the Twitter discussion got me thinking about it again.
>
> Black against #777777 passes, and black against dark orange passes, but to
> the eye, white #FFFFFF which fails, seems much more readable against this
> grey  or against this orange.
>
> There is something about black #000000 which needs a little tweak in the
> algorithm.
>
> Perhaps when black is against colour spectrum X, it requires a higher
> contrast minimum?
>
>
> Are you sure it's literally *just* full #000000 black? What about #000001?
> My point being that it's perhaps not just about that one particular color,
> but more about a particular part of the spectrum / the color space used?
>
> P
> --
> Patrick H. Lauke
>
> www.splintered.co.uk | https://github.com/patrickhlauke
> http://flickr.com/photos/redux/ | http://redux.deviantart.com
> twitter: @patrick_h_lauke | skype: patrick_h_lauke
>
>
>