turn off color to save power?

Archived from groups: comp.sys.palmtops (More info?)

In article <874qfcv6mk.fsf@jidanni.org>, Dan Jacobson wrote:
> Will my Palm (m505) start using more power the moment a non-black
> pixel is displayed? If I want to save power should I pick an
> application's black and white mode, or must I specify 1 bit color
> system wide, etc.

PDA screens don't have a 'b&w mode' and a 'color mode'. The software
driving them might, but as far as the screen is concerned it's just
displaying pixels. I think power consumption will be the same no
matter how many colors are on the screen.

--
Sincerely,

Ray Ingles (313) 227-2317

"Sure, it's easy to achieve partial obfuscation through pure
stupidity, but for complete, systematic retardation, you need
hard working great thinkers that put their best effort into
it." - Fredrik Johansson, on Windows NT

Archived from groups: comp.sys.palmtops (More info?)

Dan Jacobson wrote:
> Will my Palm (m505) start using more power the moment a non-black
> pixel is displayed? If I want to save power should I pick an
> application's black and white mode, or must I specify 1 bit color
> system wide, etc.

LCDs whether in a PDA or laptop computer or wristwatch, etc. actually
use more power when turning a pixel black although the amount of power
to turn pixels on and off is extremely small. The vast majority of
power used by a color LCD is that which is used to power the light
source.

As a test, take the battery out of your wristwatch. Notice that the
black numbers are no longer black without any power. It requires an
electric current to flow through a pixel in an LCD to straighten out
the liquid crystals thus causing light passing thru the crystal to
remain polarized in a single direction, therefore dissallowing it to
pass through the two cross polarized glass sandwiching outer surfaces.

Your color LCD only has colored pixels just as a color CRT only has
colored phosphor dots. There are no white pixels and there are no black
pixels. White is caused by all three colors red, green and blue
transmitting light to your eye. Black is caused by no light getting to
your eye.

If you want to reduce power consumption, turn off the backlight or at
least turn it down as far as you can.