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Do screen colors and background affect battery lifetime?

Continuing the discussion from Battery lifetime decreased since update v1.8:

I think this is a myth. Here is why:

Smartphones typically use one of two different display types, called OLED and LCD.
Now, this can be a bit confusing, but here is the difference:

Both types use LED (Light emitting diodes for illumination, however, their construction is different. In LCD (liquid crystal displays), a background light source is required, without it, the screen stays dark. The light from that source travels to an array of crystals in red, green and blue color, which depending of their configuration are more or less transparent. All fully transparent would be white, you get the idea? This is typically called LCD-Display, but TVs using an LED as backlight are marketed as “LED-Display” to differentiate against older models with CCFL backlight.
Why is all that important? Because with an LCD-Display, the vast amount of power is used by the backlight and only depends of the brightness of the screen, not the color displayed. That means, the power consumption should be the same, no matter what color your background or the content displayed is.

OLED displays do not need a backlight. Here the individual pixels of the screen are emitting light themselves. A complete black (“off”) pixel, does not use any power. Therefore, a dark colored background/interface uses less power that a bright one. This is why techniques like Microsofts Glance screen only work on OLED devices: By powering of most parts of the screen and only powering some pixels, these smartphones can display some content like time and date all-day without reducing battery lifetime much. This is not possible on LCD-type screens.

What does that mean for you? The Fairphone uses and LCD-screen, therefore the background of your smartphone should not affect the battery lifetime at all.

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very interesting, thanks for the info.
believing in the myth i always used dark wallpapers and set all apps that have that option to night mode (white font on black backgriund), but now i think i’ll do the exact opposite because then i can dim the background light even more and still have a quite light screen.
although the question for me is then: do apps like YAAB, that can make the display darker than the normal brightness settings do that by dimming the backlight or by making those chrystals less transparent?

My question (related to FP2 Wishlist) is: Do you believe an OLED display would be the best choice for FP2?

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Given that my research above is true - I think an OLED display might be beneficial for some applications like the glance screen. If it is the best choice overall is hard to say. It depends on how easy they are to source in good quality, the general difference in price and quality for that component and maybe even manufacturing relationships.
Given they offer the same image quality (and it seems OLED image quality is harder) and comparable priced, i would prefer and OLED display.

Maybe a bit off topic, but isn’t OLED really expensive?

I don’t know actually :slight_smile:

I have read somewhere though, that the average power consumption for OLED is higher than LED (for TV’s, anyway). I haven’t got hard figures to back that up or a source to link to so I can’t say for sure.

What is true, though, is if you want to consume less energy, turn down the brightness of your display. This will always help, both on LED and OLED displays.

This can very well be true, i just wanted to state that OLED can power
down single pixels and so reduce power when single pixels are black eg.
“off” and LCD cannot.

In the great Blog about Fairphones Environmental Impact, it is mentioned that an AMOLED screen could save energy. I was also surprised that the environmental impact of the “use” is 28% assuming a 3 year lifetime.

LCD screen
Switching to an AMOLED screen could be a potential solution for reducing carbon emission by less electricity consumption due to efficient battery usage (Lin et al., 2009), though more up-to-date research is necessary to validate this claim. On the other hand, there are not yet any studies analyzing the environmental impact of producing these screens.

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German computer magazine c’t recently had an article about this topic. Of course, still it’s just OLED displays that profit greatly from dark backgrounds. But they found that for the Razer Phone 2 with LCD, there was an increase in battery life for very dark backgrounds compared to lighter one of ~3h (from 6h to 9h of 100% screen on time).

Their explanation is that LCD nowadays dim the background light when they show mostly dark images to make black appear black and not dark grey.

Article (in German): https://www.heise.de/select/ct/2019/18/1566746569788297
Measured data: ftp://ftp.heise.de/pub/ct/listings/1918-184.zip

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