Thread Subject: 2.1-B - Luminance Contrast for Legends

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From: Robert_Nerhood@Dell.com
Date: Fri, Oct 12 2007 7:05 AM

Below is a proposal for language regarding luminance contrast for
legends.

Based on the discussion for displays, I'm proposing changing "contrast
ratio" to "luminance contrast". The Dictionary for Human Factors and
Ergonomics (ISBN 0-8493-4236-8) defines "luminance contrast" as follows:
Luminance Contrast = "a measure of the physical relationship in
luminance between two adjacent, non-specular surfaces under the same
general illumination and immediate surroundings, generally defined by an
equation similar to Cl=deltaL/L."


2.1-B - Luminance Contrast for Legends

If the legend or instructions on the device are the only means of
conveying information, then the luminance contrast shall be at least
3:1.

Note: If other means of conveying the information in the label or
instructions exists (e.g. uniquely tactilely discernible though shape
and/or location), then the luminance contrast requirement does not
apply.

Note: This requirement excludes product information labels, such as the
regulatory labels, where information can be found in other sources
associated with the product either in hard- or soft copy format.

Note: Additionally, I think we need to convey at least for computers
that there are different levels. E.G the alphanumeric labels are the
primary labels and should meet this convention; however, the secondary
functions (such as the blue numbers on an embedded numpad on a notepook)
should not meet this convention as they are infrequently used and in the
case of the numpad may add to visual clutter and additional confusion
relative to the keyboard interaction.

Please comment or provide feedback.

Thanks,

Rob

Rob Nerhood | Experience Design Group | Ergonomics Engineer
Dell, Inc. | One Dell Way | Round Rock, Texas 78682 - 7000
direct 512.723.2763
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