Re: A color tutorial from Tom Jewett

A few thoughts,

Wayne wrote: "*Has the IEEE taken any recent steps to clarify how to
compute cross platform computations of luminance?*"

I'd expand that to a) "has *anyone* taken any recent steps..." (sourcing is
less important than good data), and / but b) part of the issue with screen
luminance is that there is no "standard" for individual screens, and so any
measurement there would be tied to the tester's screen, which may or may
not be appropriate for all screens. Even if it is a pure-play
"mathematical" algorithm, it's nearly impossible to account for end-user
configurations, which will have a direct impact on "measurement versus
practical usefulness". (Walk into any Best Buy, Target or Walmart and go to
the "TV Department" - multiple screens with the same broadcast, yet color
and luminance differences are usually very obvious), and so meeting a
specific luminance value may or may not aid individual users.

Additionally, Jon wrote: "*Sufficient contrast levels are needed for a
number of vision conditions and contrast sensitivity tends to decrease with
age.  Not all people with low vision need nor want high contrast – but a
sufficient level is needed and is enough for many to access content.*"

A huge +1 there. In my training, I often recount the scenario of taking
your cell phone outdoors at lunch time and trying to access your (test)
site iunder those conditions. There, the influence of the environment
(bight sunshine) has an impact on luminance measurement and perceivability
(i.e. it is a conditional measurement). I'm not sure how we can adjust our
algorithm to address that variable.

JF

On Fri, Jun 7, 2019 at 8:58 AM David MacDonald <david100@sympatico.ca>
wrote:

>
> > I still think it is useful reassurance to test the edge cases against
> other maths that we have (e.g, Protanopia, and Deuteranopia).
>
> agreed....
>
> Is anyone aware of serious research being conducted in this area,
> including trials with significant variations of users that might result in
> proposed amendment to the algorithm? Currently, I'm unaware of any serious
> initiatives.
>
> Cheers,
> David MacDonald
>
>
>
> *Can**Adapt* *Solutions Inc.*
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> On Fri, Jun 7, 2019 at 7:19 AM Bruce Bailey <Bailey@access-board.gov>
> wrote:
>
>> > I think we are trying to help more than just colour blindness with our
>> contrast algorithm.
>>
>>
>>
>> Yes, absolutely!  I see that I did write “main purpose” below (and that
>> was a mistake), but what I really meant to be emphasizing is the genesis of
>> the formula came from addressing color blindness, where specific
>> difficulties and remediation strategies were well understood.  Then it
>> turns out that paying attention to luminosity contrast ratios helps will
>> all kinds of low vision issues.  Certainly many people do not find the
>> contrast sufficient as the ratio approaches 4.5:1.  But in terms of the
>> algorithm allowing for false positives, and in the absence of clinical
>> trials like the Lighthouse did back in the day, I still think it is useful
>> reassurance to test the edge cases against other maths that we have (e.g,
>> Protanopia, and Deuteranopia).
>>
>>
>>
>>
>>
>> *From:* David MacDonald <david100@sympatico.ca>
>> *Sent:* Thursday, June 6, 2019 3:13 PM
>> *To:* Bruce Bailey <Bailey@Access-Board.gov>
>> *Cc:* w3c-waI-gl@w3. org <w3c-wai-gl@w3.org>
>> *Subject:* Re: A color tutorial from Tom Jewett
>>
>>
>>
>> Hi Bruce
>>
>>
>>
>> I think we are trying to help more than just colour blindness with our
>> contrast algorithm.
>>
>>
>> https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html
>> <https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org%2FTR%2FUNDERSTANDING-WCAG20%2Fvisual-audio-contrast-contrast.html&data=02%7C01%7CBailey%40access-board.gov%7C9569755b82db48bc4dce08d6eab300d5%7Cfc6093f5e55e4f93b2cf26d0822201c9%7C0%7C0%7C636954451873620349&sdata=MnAIddWiPmhER2nL7q6%2F8Y2mZhuMNDl8PeZIomPduJw%3D&reserved=0>
>>
>>
>>
>> I think some people with low vision are disproportionately affected by
>> perceived low contrast.
>>
>>
>>
>> Having said that, I don't know what would need to be done to the
>> algorithm to improve it, and without, as Gregg said, significant input by
>> knowledgeable researchers, like Lighthouse did back in the day, who are
>> sensitive to the great amount of research put into our current algorithm,
>> with a proposal and a demonstration of the benefits of the improvements, I
>> wouldn't revisit the algorithm.
>>
>>
>>
>> Cheers,
>> David MacDonald
>>
>

-- 
*​John Foliot* | Principal Accessibility Strategist | W3C AC Representative
Deque Systems - Accessibility for Good
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