LCD displays in laptops

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Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Hi all, firstly am not sure if this is the right newsgroup, if not -
please point to the one that is...

I would like to establish the exact way most laptop LCD displays work in
(if any specific info re. iBook is present - it will be most welcome).

I am aware of the general theory of LCD functionality (e.g. use of
polarised filters and applying voltage to crystal molecules to untwist
them)... but... there are essentially two mode for LCD displays to work
in (http://www.altadox.com/lcd/knowledge/lcd_display_modes.htm):

positive mode - this is where BLACK is achieved by fully turning the
pixels ON (i.e. applying the voltage to them) which is kind of opposite
to the way CRT monitors work

negative mode - the opposite of positive (i.e. WHITE is the result of
fully tuning the pixel ON in terms of applying a voltage to it)...

i would like to know which mode is used by most laptops (esp macs).

This is important for a number of reasons, one of which is the default
"blackness" in some of the screensavers and autopower display managers.

Whilst displaying full black on CRT monitors actually provides power
saving and "time off" for relevant pixels, in some LCD displays this may
be actually driving corresponding pixels (i.e. the ones that display
black) fully.

Kind regards,
Leon.

 

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Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

> i would like to know which mode is used by most laptops (esp macs).
>
> This is important for a number of reasons, one of which is the default
> "blackness" in some of the screensavers and autopower display managers.

I don't know the specifics of the LCD, but when my Powerbook is asleep
and open, the screen is black and it is using virtually no power. I've
left it on and unplugged and come home from work to find the battery
>95% full.

Screensavers however are another story. Take the default Mac "flurry".
Most of the screen is dark, but it takes a lot of CPU power to create
the image. So for a portable it's best to use a low-power alternative
or just have the screen turn completely off.

If it's any consolation, my system goes from fully asleep to awake in
about 2 seconds. If just the screen is asleep, it's about 1 second. If
you put it to sleep by closing the lid, it's awake by the time you get
the lid fully open.