Re: Colour contrast algorithm when black is used

David,
I believe something like this should go into  the Understanding doc.
Yes there is an algorithm that helps one to assess more objectively
and come up with an UI that is accessible mostly but one should not
forget that WCAG 2.0 says in the first para under introduction,
"...they (i.e. the Guidelines) are not able to address the needs of
people with all types, degrees, and combinations of disability".

So maybe there could be a cautionary note or something noted as a
limitation at best with an example or two culled from the emails here
or other sources.

Thanks and best wishes,


On 8/21/17, David MacDonald <david100@sympatico.ca> wrote:
> 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 superseded this one.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
>
>
>
> *Can**Adapt* *Solutions Inc.*
>
> Tel:  613.235.4902
>
> 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*
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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
>>
>>
>>
>


-- 
Sailesh Panchang
Principal Accessibility Consultant
Deque Systems Inc
Phone 703-225-0380 ext 105
Mobile: 571-344-1765

Received on Monday, 21 August 2017 13:59:00 UTC