Edit comment LC-2545 for Accessibility Guidelines Working Group

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Comment LC-2545: Comment Shortname:; Commenter: Makoto Ueki <makoto.ueki@gmail.com> on behalf of JIS; Message-id:; Section of the document concerned:

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Commenter's response (URI):; Comment:
Will SC 1.4.1 be applied to a stacked bar chart?

For example, a stacked bar chart shows two items by using two different colors. There are the graph legends near the chart which explains what is represented by each bar and color. The patterns are not used.

It might depend on the colors used in the chart. If the colors are black and white, will SC 1.4.1 be applied to the image of the stacked bar chart?

In that case, the color differences are used to convey information within non-text content. However the patterns are not necessarily needed to convey the same information in a manner that does not depend on color. Because black and white has sufficient contrast ratio and brightness difference.

Does SC 1.4.1 require the authors to include patterns to any combination of colors?

If yes, could you explain the reason why the patterns are needed for black and white?

Proposed Change:
Need an answer from WCAG WG in order to harmonize JIS and WCAG 2.0.; Related issues: (space separated ids); WG Notes: We need a technique to make this concept clear.One needs to differentiate between "color" (hue) and lightness. For example, red and pink can be the same color with different lightness. You cannot encode information with HUE alone, but you can encode information with different lightness. So, dark red and pink are not encoded with color alone. They also differ in lightness/darkness. A light green and a dark red also differ in lightness. The formula used for contrast can be used for lightness. WCAG does not specify how different the lightness needs to be in order for them to be different lightness, because the two samples may or may not be adjacent. 3:1 is probably sufficient for adjacent blocks of color. 4.5:1 is better and 7:1 is best but you cannot have three different colors with that ratio. Patterns can be used when there are more than two or three types of information to be differentiated. We have created a new technique to make this clear. @@Add technique described at http://tinyurl.com/3vgklcg; Resolution: Yes. Lightness/darkness is independent of color and can be used to present information in a manner that is "not color alone". Black and white is an obvious example of something which is independent of color vision. Unlike WCAG requirements for foreground text against a background, there are no specific guidelines for how much lightness/darkness (or relative luminosity) contrast there should be between two items in a chart. It would seem to differ if they were separate vs if they were touching as in your example. If touching, a contrast ratio of 3:1 is probably sufficient though 4.5:1 is better and 7:1 is best (but you cannot have three different colors with that ratio. Patterns can be used when there are more than two or three types of information to be differentiated.; (Please make sure the resolution is adapted for public consumption)