Re: Color contrast principle

 Per Detlev's comment about border thickness, I remember at one point specific requirements were discussed, I think 3 pixels was one instance.  From a practical standpoint, providing a contrasting border around letters (say in a headline) could be a useful way to ensure adequate contrast for text in websites that have varying images in the background.
But it does seem as if defining adequate border thickness could be arbitrary.  Do we have any guidance for it?
Mike
    On Wednesday, January 16, 2019, 3:43:49 AM EST, Detlev Fischer <detlev.fischer@testkreis.de> wrote:  
 
 Hi Jon,I think we are roughly on to the same thing but I find the talk about points quite hard to understand (aren‘t we dealing with surfaces and (out)lines, mostly?

Sent from phone
Am 16.01.2019 um 01:24 schrieb Jonathan Avila <jon.avila@levelaccess.com>:



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I’d say something like – when determining adjacent colors to points – an adjacent point that is not immediately touching the initial point can be used for the comparison when the sum of corresponding points communicates the same information needed to identify parts of the control or graphic and its states.   That is the sum of adjacent but not touching points produces the same information necessary to identify the object.
 
  
 
Jonathan
 
  
 
From: Alastair Campbell <acampbell@nomensa.com> 
Sent: Tuesday, January 15, 2019 7:05 PM
To: WCAG list (w3c-wai-gl@w3.org) <w3c-wai-gl@w3.org>
Subject: Color contrast principle
 
  
 
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Hi everyone,
 
  
 
There was some confusion on the call about the second example under the “Adjacent colors” heading here:
 
https://cdn.staticaly.com/gh/w3c/wcag/non-text-contrast-updates/understanding/21/non-text-contrast.html?x=5
 
<image002.jpg>
 
  
 
The aim was to show a general principle of measuring adjacent colours, perhaps it needs some adjustment?
 
  
 
The principle is that: If there is a non-contrasting colour between two contrasting ones, assume that it merges with the non-contrasting colour, then does it pass?
 
  
 
In that case, assume the silver border merges into the blue background, so it is essentially white vs dark blue.
 
  
 
This is important because it meets the user-needand allows for many more design possibilities. (Designs that would fail the SC without causing an impact on people.)
 
  
 
Without that, it would essentially mean two-colour only controls.
 
  
 
There is a similar principle going on for the radio-button example (selected / not-selected) further down.
 
<image004.jpg>

  
 
All of those pass, but the middle two demonstrate the principle that if the middle contrasts with the outside, we can ignore the outer circle of the radio – it is a change of shape.
 
  
 
If anyone can think of a better explanation for the understanding doc… I’m all ears!
 
  
 
Kind regards,
 
  
 
-Alastair
 
  
 
-- 
 
  
 
www.nomensa.com / @alastc