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I read about how an LCD screen works here, and it made me wonder what actually happens when the screen shuts off. Based off of this, I can think of several possibilities:

  1. Electricity is supplied to all the pixels/crystals, thus making them all appear dark. While this fits with the on/off explanations given in that article, it seems like a significant waste of energy to use extra energy when not in use.

  2. Electricity is not supplied to all the pixels, which would light them all up, but the backlight shuts off, so the screen appears dark.

  3. Electricity is maintained to the pixels that were receiving electricity when the screen was on, but the backlight shuts off so the screen appears dark.

I would be curious to know if different phases of the off screen are different (such as a off-screen-like screen saver versus a sleep mode or being shut off, etc.).

Jo.P
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1 Answers1

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There's two different "shut off" methods: showing a black screen and actually powering off. To show a black screen, the backlight stays on but none of the pixels are energized. Light that gets polarized from the first filter doesn't change orientation (because the liquid crystals aren't energized) and so that light gets blocked by the second filter.

Turning off also de-energizes the pixels, but it also turns the backlight off. This is obviously more energy efficient, but also makes for darker black colors because the polarizing filters only stop most of the light.

Most displays will have a single light source for the backlight, but some displays, like edge-lit displays, can control regions of light and other displays use individual LEDs with each pixel. Both methods can vary the intensity of the backlight and this is sometimes called "high dynamic range" displays. You can read more about that here.

Chuck
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