Battery life and screen background?

Archived from groups: alt.sys.pc-clone.dell (More info?)

Does anyone here know if using a black background on a laptop will
improve the battery life, because the LCD won't be displaying anything
for the background? Is "black" like "off"? If 25% of the background
is showing, would using a black background be like keeping 25% of the
screen off? Or doesn't it work that way?

Thanks.

-Joel

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More about battery life screen background
  1. Archived from groups: alt.sys.pc-clone.dell (More info?)

    joel@exc.com (Dr. Joel M. Hoffman) wrote in
    news:aSHZe.13503$H24.11396@fe11.lga:

    > Does anyone here know if using a black background on a laptop will
    > improve the battery life, because the LCD won't be displaying anything
    > for the background? Is "black" like "off"? If 25% of the background
    > is showing, would using a black background be like keeping 25% of the
    > screen off? Or doesn't it work that way?


    Actually, black is "on" in a LCD. An LCD works by powering up the pixels
    to block the white light that either comes from the backlight or is
    passively reflected.

    University of Illinois at Champaign actually did a study of this once on
    an IBM Thinkpad laptop with a 14.1" LCD display. LCD power consumption
    (not counting backlight) was 1.01 Watts with a black background; 0.93
    Watts with a white background; and 0.99 Watts with the default windows
    background.

    But this difference of 0.08 Watts pales in comparison to the backlight
    itself, which is typically in the 3 to 30 watt range depending on exact
    tehnology used - Desktop LCD monitors typically used flourescent
    backlights that use 20-30 watts (or more); Laptop LCDs typically use
    electroluminescent backlights that use 3-5 watts.


    - FM -

    see also:

    http://www.crhc.uiuc.edu/
    ~mahesri/classes/project_report_cs497yyz.pdf#search='lcd%20backlight%
    20power%20consumption'
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