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In the smartphone market the majority of displays are either AMOLED or LCD, but many people don't know that the wallpaper color you choose, yes, wallpaper, can actually make a difference to your smartphone battery life depending on the type of screen with which your device is equipped. Pure black wallpaper, or a dark-colored background in general, can actually save you a significant amount of battery life.

Display tech explained: LCD

LCD stands for Liquid Crystal Display and it's the same kind of technology you'll find in your televisions, monitors and so on. As the name suggests, Liquid Crystal Displays are actually crystals, and as such, they don't emit light of their own but rather transmit light from a light source behind them.

This means that even if you're looking at black on your smartphone or tablet screen, it is actually black lit up from behind. Therefore, LCDs don't really display "true" black

Display tech explained: AMOLED and OLED

Next, AMOLED. AMOLED stands for Active-Matrix Organic Light-Emitting Diode and it is also used for televisions screens but more notably, for smartphones. OLED displays are similar, but do not use an Active Matrix.

Samsung displays, for example, are usually AMOLED: the Galaxy S5, Galaxy Note 3 and Galaxy Note 4 all use an AMOLED display. The LG G Flex 2 uses a Plastic OLED display and the Google Nexus 6 also uses an AMOLED screen.

As the name implies, the screen is made up of organic material that actually produces light when a current is passed through it – electroluminescence. Because AMOLED displays can be lit up pixel by pixel like on the Moto X, black is "true" black because there is no back-lighting.

This also means AMOLED displays are easier on your battery because every pixel is not always lit up.

Battery life: AMOLED vs LCD

AMOLED

You can probably see where this is going: if you have an AMOLED display then you can actually save some battery life by using black wallpapers, or generally darker wallpapers and themes.

little experiment and figured out that you can save about 6% battery life/hour at 20% brightness by using a black wallpaper on an AMOLED display, and about 8%/hour at full brightness.

These results are based on an always-on screen, but the basic theory is sound even if the figures are not exactly set in stone. Another tester using a different method came up with a general 18% saving all day.

LCD

What about LCD battery saving wallpaper, I hear you ask? Sorry, LCDs rely on back-lighting, so there's nothing you can do to save battery there.

The only thing you can do is set your device settings to Battery Saver mode and try not to turn your screen on all the time. Keep your display brightness as low as possible and your screen timeout nice and short.

The good news is you can have the brightest colored wallpaper and themes imaginable and it won't make a difference to your battery. Just think about that when you look at the gloomy screens of AMOLED owners clinging to extended battery life (just don't stray too far from a charger while you gloat).

Other battery life tips for AMOLED screens

There are other things AMOLED owners can do to maximize their battery life too, like setting as many app themes to be as dark as possible.

If you can change the appearance of a bunch of apps you use frequently (or download a different app that does the same thing but that does allow appearance customization), you can save even more battery life.

After all, we don't spend all day on our home screens but more time in apps. You can also set your text and email preferences to be black background and white text, depending on your device and chosen apps.

The easiest way to figure it out for yourself is to fully charge your device as is and wait until it's almost totally dead and look at how much of your battery was used by the display. Just go into your Settings menu and look under Device Settings for Battery.

Make a note of the percentage your display has used up, then, while recharging your phone, switch to a black wallpaper and repeat the cycle to see the difference.