Thread Subject: Revised 2.1.A

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From: Robert_Nerhood@Dell.com
Date: Thu, Oct 18 2007 3:05 PM
Subject: Revised 2.1.A

Revised proposed language for Luminance Contrast Ratio for Display.
Discussion indicated some confusion with this requirement which involves
direct light measurement and the Contrast Ratio used in SW/Web that is a
calculation based on RGB values.

Discussion or comments?

2.1-A - Luminance Contrast Ratio for Display

For displays on products, at least one mode must exist where the
contrast ratio between the luminance at light state compared to
luminance at dark state shall be at least 5:1.

Note: Light (or high) state typically refers to the lighter condition
for the display. For example, white content/background on an LCD. Dark
(or low) state typically refers to the darker condition for the display.
For example, black content/background on an LCD.





Rob Nerhood | Experience Design Group | Ergonomics Engineer
Dell, Inc. | One Dell Way | Round Rock, Texas 78682 - 7000
direct 512.723.2763
This communication and all attachments are confidential and may be
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From: Gregg Vanderheiden
Date: Fri, Oct 19 2007 12:20 AM
Subject: Re: Revised 2.1.A

Robert



I think we need to define 'contrast ratio' here so it doesn't inherit
the definition from software content since this is real luminance. Do we
want to use the same formulae we have been talking about for labels?
(e.g. use "luminance contrast" and use (L1-L2)/L2 with minimum
L1 )



Or do you want to use the contrast ratio (L1 + 0.05) / (L2 + 0.05)





Gregg
-- ------------------------------
Gregg C Vanderheiden Ph.D.






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Sent: Thursday, October 18, 2007 4:03 PM
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Subject: [teitac-hardware] Revised 2.1.A

Revised proposed language for Luminance Contrast Ratio for Display.
Discussion indicated some confusion with this requirement which involves
direct light measurement and the Contrast Ratio used in SW/Web that is a
calculation based on RGB values.

Discussion or comments?

2.1-A - Luminance Contrast Ratio for Display

For displays on products, at least one mode must exist where the contrast
ratio between the luminance at light state compared to luminance at dark
state shall be at least 5:1.

Note: Light (or high) state typically refers to the lighter condition for
the display. For example, white content/background on an LCD. Dark (or low)
state typically refers to the darker condition for the display.

For example, black content/background on an LCD.

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

This communication and all attachments are confidential and may be legally
privileged. If you are not the intended recipient, (i) please do not read
or disclose any content to others, (ii) please notify the sender by reply
mail immediately, and (iii) please permanently delete this communication
from your system. Failure to follow this process may be unlawful and
subject to prosecution. Thank you for your cooperation.

From: Robert_Nerhood@Dell.com
Date: Fri, Oct 19 2007 6:50 AM
Subject: Re: Revised 2.1.A

Contrast ratio in this case is the luminance of the bright state (white
screen) divided by luminance of the dark state (black screen). In
talking with the LCD engineers here, they will take anywhere from 5 to
13 measurements across the display and utilize the averages for each
state to calculate the contrast ratio.







From: = EMAIL ADDRESS REMOVED =
[mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of Gregg
Vanderheiden
Sent: Friday, October 19, 2007 1:15 AM
To: 'TEITAC desktop/portable (hardware) subcommittee'
Subject: Re: [teitac-hardware] Revised 2.1.A



Robert



I think we need to define 'contrast ratio' here so it doesn't
inherit the definition from software content since this is real
luminance. Do we want to use the same formulae we have been talking
about for labels? (e.g. use "luminance contrast" and use
(L1-L2)/L2 with minimum L1 )



Or do you want to use the contrast ratio (L1 + 0.05) / (L2 +
0.05)




Gregg
-- ------------------------------
Gregg C Vanderheiden Ph.D.