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RE: onscreen font sizes

From: Adam Cooper <cooperad@bigpond.com>
Date: Sun, 4 Mar 2012 12:01:25 +1100
To: "'Felix Miata'" <mrmazda@earthlink.net>, <w3c-wai-ig@w3.org>
Message-ID: <000901ccf9a2$52e94820$f8bbd860$@bigpond.com>
Hi Felix,

Thanks for your response.

I unreservedly apologise in advance if this has been covered in this forum
previously or is treated elsewhere, and for what is no doubt the result of
my naivety.

Yes, I agree - the flexibility of web technologies and using relative sizing
for fonts is a critical factor in improving accessibility.

But the reason I ask is that for success criteria 1.4.3 and 1.4.6, there are
requirements for colour contrast at thresholds of 18pt normal and 14pt bold.
How are these font sizes determined onscreen, especially when text sizing
sufficient techniques for 1.4.4 stipulate relative units for font sizes? 

So, for example, a user is viewing a page in IE8 at 1024 x 768 on a 19" LCD
with the default UA style sheet font size of 12pt, but the web page includes
a CSS specification of 0.8em  and no bold for paragraph text.  How is it
possible to determine whether the colour contrast ratio meets the success
criteria when it is not possible to determine the onscreen font size in
points?  Am I to assume that the font size is 0.8 x 12 or 9.6 points?

With regards to the utility and possibility of comparing onscreen font sizes
with print, I have been asked by clients a number of times how to ensure
that font sizes are 'the right' size for people with low-vision to which the
only thing I can say is 'use relative sizes and don't specify font sizes
below 1em or 100% so that the user can change as per their desire' ... which
is usually greeted with a blank look and some reference to a document from a
vision-loss organisation that says something like 18pt is recommended for
people with low-vision. 

Or am I missing something?

Cheers,
Adam 

-----Original Message-----
From: Felix Miata [mailto:mrmazda@earthlink.net] 
Sent: Sunday, March 04, 2012 11:01 AM
To: w3c-wai-ig@w3.org
Subject: Re: onscreen font sizes

On 2012/03/04 10:22 (GMT+1100) Adam Cooper composed:

> I am seeking a tool for calculating on screen font sizes that takes 
> viewport size, resolution, monitor pitch, browser defaults,  and 
> specified font sizes etc. into consideration ... something whereby I 
> can enter these variables, crank the handle, and come up with a result 
> that provides a useful comparison to printed font sizes. Does anyone know
of this holy grail?

REM & EM http://www.w3.org/WAI/GL/css2em.htm
http://www.w3.org/TR/css3-values/#font-relative-lengths

The magic is that the user is in position to customize his personal
computing device if and when he finds the base font size in his browser is
inappropriate. No designer is in position to do better, no matter how many
things he might fetch from the DOM. The designer who sticks to sizing only
contextually, leaving the base size at the user's specification, is doing
the best job for accessibility.

The relationship to print isn't necessarily useful. A major advantage of the
web is the absence of necessity to fit content to a known size of output
medium. Browsers inherently adapt to the wide variation of available
viewport space in users' agents. Web user space adapts to user needs in ways
no other medium can compare to. Web designer use of CSS typically limits
that adaptability, reducing accessibility as a result.

IOW, if you resist the temptation to try to make the web look like
cookie-cut magazine pages, you maximize accessibility, and user experience.
--
"The wise are known for their understanding, and pleasant words are
persuasive." Proverbs 16:21 (New Living Translation)

  Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/
Received on Sunday, 4 March 2012 01:02:00 GMT

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