Technology – Is a black pixel on or off?

Bright Lights (Tech Radar)

[Note: This post is random post about Light Emitting Diode (LED). For more startup related messages, visit our main site.]

In a recent Techzing Podcast the guys spoke about the deceptively inefficient Yelp rating system. On a unrelated topic they briefly raised the question: is a black pixel on or off?

The curiosity got the better of us and we spent some time googling the answer. In summary LED turn the pixel off to display black. However in older display technology, the answer differs. We share the results below.

Pre-Flat – Blocks Light:

In the world before flat screens, screens had a big flat light at the back that was always on.

“If a pixel wanted to show you white it lets all the light through. If it wants to show you black it blocks all the light. Either way, the light behind is still on and still consuming the same power.”

(Source: Steve Mould)

LCD – Blocks Light:

“Liquid Crystal Display (LCD) pixels do not produce there own light. If the pixels are off, they don’t let the backlight through, when they are on, they let the backlight through.”

(Source: About.Com)

AMOLED – Turns Off:

To display black, AMOLED (active-matrix organic light-emitting diode) turns off the pixel. As a result you can save your battery by displaying black.

(Source: Wikipedia)

For more information you can visit the Nokia Developer site for their study on how color makes a difference.

Steve Mould test the hypothesis with some impressive calculations. His post How much phone battery can you save by switching to dark wallpapers and themes? provides an insight into extending the life of your phone battery.

We are not scientists, so drop us a line if we have mixed up the facts!


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