- From: Repsher, Stephen J <stephen.j.repsher@boeing.com>
- Date: Wed, 14 Jun 2017 17:24:15 +0000
- To: Alastair Campbell <acampbell@nomensa.com>, Glenda Sims <glenda.sims@deque.com>, public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
Hey Alastair, I can certainly understand folks without low vision having an intuition different from those who do. That happens all the time. I told my wife when we first met that she'd never understand my vision. Being a nurse, she was not happy I said that. A few months or so into dating, she realized I was right. If we can't find peer-reviewed research on what the contrast needs to be, then perhaps just anecdotal or survey data from people with low vision would suffice. I think we need to follow the logic from the opposite end to and say with certainty that people with low vision or color blindness need more contrast than the average viewer. Since low vision is a spectrum with many variables, there isn't going to be a single number that works for everyone (or even every type of graphic for that matter). So as with other SCs, the choice will either be limited by the users (e.g. satisfies 95% of LV) or by an upper limit for developers (e.g. too few color choices). I'm betting we'd hit the latter limit way before the former one, so we should concentrate some effort there as well. Getting back to the bar chart example, you wrote: > It doesn't solve the problem, in that case the colours all need to be at the opposite end of luminance from the border, which cuts it down the choice of different colours a lot. Or you have to separate the bars. No, that's not the case and this is where things get confusing and the SC as written now gets deficient. The user requirement is to be able to distinguish bars from adjacent ones and from the background, but from their own border is irrelevant. If I had a bar chart with 3 bars, I could have a black border with a white background, and then fill the bars with black, 20% gray, and white, making all important contrast ratios over 4. We need to work on how to state this better in the criterion. Steve -----Original Message----- From: Alastair Campbell [mailto:acampbell@nomensa.com] Sent: Wednesday, June 14, 2017 11:54 AM To: Repsher, Stephen J <stephen.j.repsher@boeing.com>; Glenda Sims <glenda.sims@deque.com>; public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org> Subject: Re: Please vote on proposed WCAG 2.1 SC for Color Contrast of User Interface Components [Steve] Yes, my point was just that arguments for or against need to be based on either common knowledge or logic, or research. Saying text is harder doesn't pass the former. Hi Steve, I think we need some examples then, because (as someone who's vision is just about corrected to 20/20 with glasses), it does appear logical that lines and blocks are easier to perceive than equivalently contrasting text. I can only state that from personal experience, perhaps it is different with low-vision (rather than it being a smooth acuity continuum). Taking the attached map screenshot, the white roads next to the grey blocks are not great for contrast, but sizing plus gestalt perception makes them easier to perceive than the small text. [Steve] I'm just going to have to disagree. I strain my eyes all the time viewing things like this, and a map with tons of lines and labels is actually a perfect example. [AC] And it is the lines, not the labels? It seems logical to people without low-vision that lines & blocks would be easier, so we either need examples to demonstrate why it isn't, or some research (even if we have to do it ourselves). [Steve] On a bar chart, for example, a bar may need to be distinguished from 3 adjacent colors (2 bars on either side and the background). A thin border with good contrast to the background solves the problem and then any color for the bars passes. It doesn't solve the problem, in that case the colours all need to be at the opposite end of luminance from the border, which cuts it down the choice of different colours a lot. Or you have to separate the bars. For example, on the last example here: https://github.com/w3c/wcag21/issues/9 The pie chart has to 'explode' (i.e. the slices have gaps between them) and one of the lighter slices needs a border as well. Cheers, -Alastair
Received on Wednesday, 14 June 2017 17:25:02 UTC