- From: Chris Lilley <chris@w3.org>
- Date: Fri, 18 May 2007 03:01:28 +0200
- To: "Loretta Guarino Reid" <lorettaguarino@google.com>
- Cc: public-comments-WCAG20@w3.org
On Friday, May 18, 2007, 1:28:55 AM, Loretta wrote: LGR> Dear Chris Lilley , LGR> PLEASE REVIEW the decisions for the following comments and reply to LGR> us by 7 June at public-comments-WCAG20@w3.org to say whether you are LGR> satisfied with the decision taken. Note that this list is publicly LGR> archived. I am fully satisfied by your responses to both of my comments. Thank you for making hose changes. LGR> ---------------------------------------------------------- LGR> Comment 1: LGR> Source: http://www.w3.org/mid/20060522154433.CF78166363@dolph.w3.org LGR> (Issue ID: LC-580) LGR> Part of Item: LGR> Comment Type: TE LGR> Comment (including rationale for proposed change): LGR> The term "luminosity" is incorrect here (it applies only to certain LGR> Broadcast video signals). Relative luninance is the correct term. When LGR> used as a ratio, the difference between absolute and relative LGR> Luminance can be dropped, but the term luminance rather than LGR> luminosity should be used. LGR> http://www.w3.org/TR/2006/WD-WCAG20-20060427/appendixA.html#luminosity-contrastdef LGR> defines the coefficients for calculating luminance, and its good to LGR> see that the Rec.709 chromaticities are used (rather than, for LGR> example, the NTSC ones which do not apply to modern computer monitors LGR> at all). (the coeeficients are correct, see the "luminanceToAlpha" LGR> section of http://www.w3.org/TR/SVG11/filters.html#feColorMatrix but LGR> the specification does not explain why this is so. LGR> However the text as it stands implies that the formula given is LGR> universally applicable. it is not. This is particularly importnt when LGR> printing Web materials. LGR> Proposed Change: LGR> change "luminosity" to luminance throughout. LGR> change "The luminosity of a color is defined as" to "the luminance of LGR> an sRGB color is defined as". LGR> change "blue RGB values" to "blue sRGB values" (the equation does not LGR> apply to other color spaces). LGR> Remove the exponentiation operator and the 2.2 gamma approximation. LGR> Instead, use the correct sRGB transfer curve. LGR> Reference the sRGB specification. See the SVG 1.2Tiny specification LGR> for an example of how to reference it. LGR> You may want to note that the equation given is only correct for LGR> typicalcolor vision (the ISO standard observer). For atypical color LGR> vision, often incorrectly termed color blindness, different equations LGR> apply depending on the type of atypical color vision and the degree LGR> of severity. LGR> For more information, please see LGR> http://www.w3.org/Graphics/atypical-color-response LGR> ---------------------------- LGR> Response from Working Group: LGR> ---------------------------- LGR> Thanks for the comments and suggestions. To take them each in turn: LGR> CL: change "luminosity" to luminance throughout. LGR> Since Web content doesn't provide any light output (HTML doesn't give LGR> off photons) we can't use the word "luminance" (which means light LGR> output). However 'relative luminance' is used in the literature for LGR> the concept we are describing and we are now using this. Okay. LGR> CL: change "The luminosity of a color is defined as" to "the luminance LGR> of an sRGB color is defined as". LGR> See above regarding luminance. And, we have switched to specifying LGR> that we are talking about sRGB in our equations. Good. LGR> CL: change "blue RGB values" to "blue sRGB values" (the equation does LGR> not apply to other color spaces). LGR> Correct and we have done so. LGR> CL: Remove the exponentiation operator and the 2.2 gamma LGR> approximation. Instead, use the correct sRGB transfer curve. LGR> Done. Now uses the equations from the W3C document on sRGB. Thanks. LGR> CL: Reference the sRGB specification. See the SVG 1.2Tiny LGR> specification for an example of how to reference it. LGR> Done LGR> CL: You may want to note that the equation given is only correct for LGR> typical color vision (the ISO standard observer). For atypical color LGR> vision, often incorrectly termed color blindness, different equations LGR> apply depending on the type of atypical color vision and the degree of LGR> severity. For more information, please see LGR> http://www.w3.org/Graphics/atypical-color-response. LGR> We have explained this briefly in our "Understanding" document. A LGR> longer exposition of this will be released in a paper (since it is too LGR> complicated to put into How to Meet SC 1.4.3 itself. Agreed. LGR> The contrast LGR> ratios were set higher than normal and in a way to account for low LGR> vision and atypical color vision. LGR> The paper "Atypical colour response" has also been added as a resource. Thank you! LGR> You can find the updated SC and definitions at LGR> http://www.w3.org/TR/2007/WD-WCAG20-20070517/#visual-audio-contrast-contrast LGR> and LGR> http://www.w3.org/TR/2007/WD-WCAG20-20070517/#visual-audio-contrast7 LGR> . LGR> The Understanding SC 1.4.3 and 1.4.5 documents can be found at LGR> http://www.w3.org/TR/2007/WD-UNDERSTANDING-WCAG20-20070517/#visual-audio-contrast-contrast LGR> and LGR> http://www.w3.org/TR/2007/WD-UNDERSTANDING-WCAG20-20070517/#visual-audio-contrast7 LGR> . LGR> ---------------------------------------------------------- LGR> Comment 2: LGR> Source: LGR> http://www.w3.org/mid/20060522155848.9BF2ADAE7D@w3c4-bis.w3.org LGR> (Issue ID: LC-581) LGR> Part of Item: LGR> Comment Type: TE LGR> Comment (including rationale for proposed change): LGR> "3.2.2 Changing the setting of any form control or field does not LGR> automatically cause a change of context (beyond moving to the next LGR> field in tab order), unless the authored unit contains instructions LGR> before the control that describe the behavior" LGR> Consider a user interface for a map, where form fields such as panning LGR> controls, layer selections or search boxes are used to zoom,pan, or LGR> alter a map. This common use seems to be precluded by the text above. LGR> Proposed Change: LGR> I regret not being able to suggest suitable text at this time. I can LGR> see the benefit of what you are trying to do, and I can see that it LGR> makes non-confomant some interfaces that are currently used. I think LGR> the text needs to be more precise, and look forward to discussing this LGR> further with you. LGR> ---------------------------- LGR> Response from Working Group: LGR> ---------------------------- LGR> User interfaces that allow the user to select different views of the LGR> same data cause changes in content, but not changes in context. Ah, okay. LGR> Success Criterion 4.1.2 has been changed to require that user agents LGR> and assistive technology be notified of the changes in state produced LGR> by such changes in views. That works for me. -- Chris Lilley mailto:chris@w3.org Interaction Domain Leader Co-Chair, W3C SVG Working Group W3C Graphics Activity Lead Co-Chair, W3C Hypertext CG
Received on Friday, 18 May 2007 01:02:03 UTC