Re: Changing definition of "Large text" to use px rather than pt

I did make a mistake.  I used dpi instead of resolution. DPI would do it
for absolute size, but monitor resolution doesn't.

I will make constructions to test the parameters you suggest.

As we finish our style picker this summer we will include a method to enter
the monitor size. Calculating an absolute font size from monitor size and
resolution is not too difficult.  Most monitors are very close to 30/60/90
triangles relative to the diagonal.

Wayne

On Mon, Apr 25, 2016 at 10:14 AM, Patrick H. Lauke <redux@splintered.co.uk>
wrote:

> Additionally, worth pointing out: this exact problem (the inability of an
> author to have influence over the exact physical size as measured on screen
> of what they define in CSS etc) will also come around the same way if the
> Low Vision TF tries to define a baseline minimum font size. So having a
> shared understanding of what can actually be mandated in the SC (rather
> than running the danger of mandating something that simply can't be
> consistently achieved/tested by authors) is essential even here, or we'll
> be circling the same discussion at that point too (similarly, I've already
> been around this whole discussion in the mobile a11y TF when defining touch
> target sizes and adding qualifiers to any measurements there).
>
> P
>
>
> On 25/04/2016 18:05, Patrick H. Lauke wrote:
>
>> Copying this to the list, rather than making an off-list discussion of
>> this:
>>
>> On 25/04/2016 17:11, Wayne Dick wrote:
>>
>>> Dear Patrick,
>>> I do understand the current need to use relative font sizes, but
>>> legibility cannot be addressed with relative sizes. For normal readers
>>> you need to fit between 7-15 letters in the foveal region of the retina.
>>> For readers with partial signt you usually need much higher settings to
>>> make up for not using the fovea effectively. So to get projections of
>>> that size on the retina from 40cm you need specific physical sizes.
>>>
>>> The contrast settings are based on visual acuity measures that influence
>>> an individual's contrast sensitivity. Again this requires specific
>>> angles to subtend the retina.
>>>
>>> So, I our next go around we do need to include physical size of the
>>> print or our contrast ratios are meaningless. We may conclude that for
>>> certain screen sizes and dpi there is an acuity range necessary for
>>> visual access.
>>>
>>
>> My point is that there is no way that an author can know, or even set,
>> the physical size that any measurement they set (in their CSS, whether
>> using px or pt or mm or any other unit of measure) will actually render
>> as in physical sizes.
>>
>> So we need to anchor this somewhere.
>>
>> The assumption needs to be made that the default user agent base font
>> size is baseline readable (otherwise the user will need to use a
>> different device, change user agent, change their OS). If that is not
>> the case, and the user has a device where 16px (the common default user
>> agent font size) is not legible, then that cannot be the concern of the
>> author (as the author has no way of knowing this, nor influencing this
>> only for that particular user).
>>
>> Here are some guidelines. Depending on the language, words have an
>>> average length of from 10 to 15 letters with longer words occuring about
>>> 2% of the time. A device should fit most words on one line for genuine
>>> readability. Thus if you read English and need letters of 1.25cm (36pt)
>>> letters a you need at least a screen width of 12.5cm (5in). That means a
>>> diagonal of 25cm (10in)
>>>
>>
>> This does not take into consideration user agent or OS settings for
>> zoom, screen size, dpi adjustments that are made automatically, or
>> particular viewport settings specified by the page and how the UA/OS
>> react to them.  You can't have an SC that
>>
>> My mobile phone is 15cm diagonal and 7.5 on its portrait width. I can
>>> use it for visual reading some. I cannot read most web pages visually.
>>>
>>
>> This is anecdotally interesting, but it would be more helpful to see
>> what the exact font size of those pages that you can't read is set to,
>> and whether or not those pages set the browser into using the ideal
>> viewport (with viewport meta of width=device-width).
>>
>> 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
>
>