
Dark vs. Light Theme Battery Stats on SAMOLED  - mozami
http://forum.xda-developers.com/showthread.php?t=1882467
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exDM69
This was measured using the battery status indicator in Android, with periods
of ten-twenty minutes and the results were extrapolated. This is not at all an
accurate way to measure power consumption. You need to use multimeter and
measure real current going to the screen. Or for "real world" battery life
results, you'd need to let the battery recharge and then drain all the way,
not let it run for 20 minutes, then use a very inaccurate battery status
indicator and finally extrapolate.

xda-developer forums seem to be full of tips and tricks that make your Android
device battery last longer or the device work faster, but a lot of that stuff
is just crap. This article was better than average, but the results are still
very convincing.

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mtgx
What has always puzzled me is that I thought Google made stock Android pretty
dark-themed because they wanted to help manufacturers that used AMOLED
screens, specifically Samsung, who makes like 95% of AMOLED's - and yet
Samsung has chosen to use a very light-themed Touchwiz skin. It makes no
sense. You'd think they would be the first to want to take advantage of a
darker theme with their Super AMOLED flagship devices with large screens.

~~~
micampe
Maybe, having the real data on power usage from the components instead of a
script reading a non linear, corrected and unreliable indicator, they know it
doesn't matter as much as XDA thinks.

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bkumar86
there seems to be a lot of confusion over the efficiency of amoled vs lcd. In
lcd, the power consumed directly depends upon the brightness, basically LED's
provide the back-light light source and the colors you see on the screen are
the representative of the kind of filters the light from the LCD had to cross
to reach the surface. All lcd's are in this way passive displays. In an AMOLED
display, there are three sets of actual LED's per pixel visible on screen.
Each of the led making up a pixel can be individually be turned on or off,
resulting in a display color, resulting in the infinite contrast and brighter
colors. The current technology restricts the brightness of each of those tiny
led's resulting in a lower brightness, and also the individual tiny led's
brightness varies over the life of the panel. this is the biggest shortcoming
for an AMOLED.

When you see a picture of light on an AMOLED screen, it is actually true that
a physical light is being prepared in front of your eyes on the screen by
adding the three colors in proportion. this is not an easy task and so
explains why lcd's as of now display truer colors. This truly is a modern
technical achievement.

~~~
alok-g
>> this is not an easy task and so explains why lcd's as of now display truer
colors

OLEDs have better color gamut and contrast than LCDs (without local dimming),
making the colors better than LCDs.

~~~
micampe
OLEDs have _larger_ color gamut, but larger is not always better.

 _“The Color Gamut is not only much larger than the Standard Color Gamut,
which leads to distorted and exaggerated colors, but the Color Gamut is quite
lopsided, with Green being a lot more saturated than Red or Blue, which adds a
Green color caste to many images. Samsung has not bothered to correct or
calibrate their display colors to bring them into closer agreement with the
Standard sRGB / Rec.709 Color Gamut, so many images appear over saturated and
gaudy.”_ – <http://www.displaymate.com/Smartphone_ShootOut_2.htm>

~~~
bkumar86
what i meant to explain was, this.. the LED's fade over time. hence their
color changes over time. and making two LED's display the same color and
making them time equally is a very challenging job, some thing which current
day technology is unable to do. yes, led's have a bigger color gamut, but the
accuracy is definitely to b improved. gamut is the range, while accuracy is
the exact color required i.e precision

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Steko
Spoilers: a very impressive +3 hours of screen time by using dark themes
instead of bright ones on SAMOLED.

Minor tangent: I'm not sure how he defends his contention that SAMOLED > LCD
by noting that he didn't test anything but SAMOLED in the comments. I realize
he wasn't testing anything else and I'm perfectly willing to believe that
SAMOLED is more efficient but he still claimed X and when asked for evidence
punted.

~~~
megablast
>I simply timed how long it took the battery to drain 5% with the screen
always on at various brightness levels and while viewing an all white or all
black 720p image fullscreen in QuickPic.

This is absolutely best case scenario, ignoring all other battery factors.

~~~
jug6ernaut
Best case scenarios for time, but honestly thats not what is important in
these stats. Rather its the % difference between the two. The total life of a
cell phone will always be different between devices/users, the % difference
solely from the bright/dark difference should stay generally the same.
Assuming most of the time is spent going through the UI(which is doubtful
tho).

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aw3c2
did he run it multiple times? was the battery recharged between each test? how
did he make sure the 5% were actually always the _same_ 5% and comparable?

~~~
monochromatic
They weren't. Look at the battery ranges in his spreadsheet.

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alok-g
Amongst OLED and LCD displays with everything else (size, resolution, etc.)
OLEDs intrinsically consume a lot more power than LCDs. Using dark themes help
for OLEDs for reasons already stated here, and from what I have seen working
on the display industry for several years, the power numbers quoted by OLED
display manufactures often presume a dark theme when comparing power to LCDs.

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kqr2
This reminds me of Blackle : the black front end to Google Custom Search which
claims to save energy when using CRT monitors.

<http://blackle.com/>

<http://en.wikipedia.org/wiki/Blackle>

~~~
artmageddon
I remember these findings being refuted, and I thought it was because it took
the same amount of power for an LCD screen to show a black pixel instead of a
white pixel.

I will say, given these findings from OP, I hope these types of displays
become more common.

~~~
keenerd
It takes more energy for an LCD to show a black pixel. It is not much compared
to the backlight, though. On one of my laptops solid black uses 0.5 watts more
than solid white.

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subsystem
Switching to a dark theme and lowering the brightness also works quite good
for desktops on UPS.

~~~
arrrg
Lowering the brightness? Sure. Switching to a dark theme? Not so much.

If you are using a LCD the color of your pixels doesn't matter. Ok, it might
matter a little bit but not much and it's not as easy as saying that white
uses more power than black. It might even be the other way around.

In an LCD the color is determined by a liquid cristal filter that can be
turned on or off and dimmed. The filter itself needs hardly any power,
however. Not compared to the actual light that shines through that filter.

The light comes from LEDs or CFLs (I guess in principle you can use any light
source but those two have useful form factors and need less power than, say,
incandescent lightbulbs) behind that filter. And that light is always on. Some
TVs have local dimming to make the blacks blacker in certain regions of the
image, but computer monitors don't.

So by using a dark theme, all you influence is the filter, not the actual
lights. As you might know, covering up a lightbulb so you don't see it's light
anymore doesn't magically make the lightbulb consume no more power.

AMOLED displays work differently. There the pixels themselves light up or
don't. They are like a matrix of thousands of minuscule lightbulbs you can
individually turn on or off.

~~~
dbaupp
Don't forget CRTs! ;) Using a dark theme reduces their power usage.

<http://i.stack.imgur.com/c6yrk.jpg> (From here,
[http://skeptics.stackexchange.com/questions/4373/does-a-
webp...](http://skeptics.stackexchange.com/questions/4373/does-a-webpage-with-
a-black-background-save-energy))

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lucian1900
I just find dark themes less objectionable. I'll always choose one if it's
available.

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est
This also applies to plasma TVs afaik

