Would I be correct in the assumption that if you have a program in which you can change the program's appearance, would it consume more battery power if the appearance has more "lit" pixels than "dark" or "unlit" pixels?
For example, I use a calendar program called ThumbCal. It comes with numerous skins. For the purpose of this discussion, let's assume that there are only two skins. One skin is basically a white background with black lettering, while the other is a black background with white lettering.
Clearly, the one with a white background is considerably brighter than the one with a black background. Both are equally legible, but the white background is brighter because more pixels are lit to display the white background.
My question is this, will the program use MORE battery power if the white background skin is used? It seems logical because more pixels are lit, or on.
Am I right?
Thanks,
Peter
No. On an LCD screen, like the HD2 has, there is a uniform backlight under the screen, white pixels let that light through, while black ones block it. Even on a full black image, the same amount of light is still generated, only to be blocked and dissipated in the screen just afterwards. So, consumption is independent of the displayed image.
It would be true on an OLED display, where each pixel is indeed an independent light source.
kilrah said:
No. On an LCD screen, like the HD2 has, there is a uniform backlight under the screen, white pixels let that light through, while black ones block it. Even on a full black image, the same amount of light is still generated, only to be blocked and dissipated in the screen just afterwards. So, consumption is independent of the displayed image.
It would be true on an OLED display, where each pixel is indeed an independent light source.
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Great explanation, and completely understood. Thank you.
Peter
Related
Is there a way tio get a clock in the screensaver? my just turns totally black.. in my old nokia and SE it was possible to put a clock in there.. i have tried but cant find anything about it.. / Jörgen
It's not a screensaver, that's the screen being turned off to save battery. My guess is that on smaller screens the power drain involved in displaying the clock is quite low as the backlight wasn't on. On the screen on the hero (and pretty much every other colour screen phone brought out in the last 5 years) the screens need to be backlit to show anything and the power drain would be huge.
In short, there might be an application to do it but you are far better off just pressing the on button when you want to see the time.
herman3101 said:
On the screen on the hero (and pretty much every other colour screen phone brought out in the last 5 years) the screens need to be backlit to show anything
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Really? Why is that?
Modern LCDs all have a backlight and the image you see is obtained by filtering this light through individual switchable filters (these make up the pixels). In the past some screens worked by varying how light is reflected from the screen using these filters but these are inferior to modern lcds. We are now seeing a return to non-backlit screens with the new OLED technology but this is still actively lit at the individual pixel level.
If you don't believe me then take apart a laptop or LCD screen and disconnect the power inverter which is responsible to supplying the power to the backlight. The screen will appear to be completely dark unless you shine a very bright light on it and then you will be able to see the image very faintly. Just don't do what I did and snap the inverter, felt very silly.
I really like the GTX version of NRGZ28's CHT rom, but it strikes me that with all that wite in the screen it will use more power.
Can anyone confirm that's the case?
cheers
hmm maybe I missed something but why would a color cause more battery drain.
you could also use the leocpuspeed to unclock your cpu thus saving some power.
griZlyadams said:
I really like the GTX version of NRGZ28's CHT rom, but it strikes me that with all that wite in the screen it will use more power.
Can anyone confirm that's the case?
cheers
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Technically, your assumption is not correct. Your HD2 comes with an LCD, displaying the white color does not affect power consumption here.
In an LCD, the backlight is always on when contents are displayed - power consumption is only reduced if you dim the backlight, or the device goes into standby mode.
In a simple description: The LC molecules actually turn like a shield to let the backlight through or not. Each pixel on the screen is divided into three subpixels (red, green, blue) to produce the colors.
If one pixel (eg all subpixels) gets the full shield, it shows black - but the backlight is actually still on.
In the sum: Maybe the power consumption with your new theme goes up just because you look at it more often... isn´t that a funny side effect?
From my understanding of how LCD screens work the backlight is permanently on and energy is used to block the light coming through the colour pixels thus more energy is used to produce a black screen than a white screen!
johnk1973 said:
From my understanding of how LCD screens work the backlight is permanently on and energy is used to block the light coming through the colour pixels thus more energy is used to produce a black screen than a white screen!
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That sounds interesting. Any source for that?
makes sense (no pun intended !), for some reason I had it in my head that these were amoled screens.....wishful thinking I guess!
Yes, black uses more power on this type of screen (on a CRT it's reversed, the black uses less power than white). But you won't notice any real gain (a few minutes a day at best) since the power hungry part is the backlight, and because when the device isn't in standby you are probably using it (I'm not someone who look at the home screen and do nothing more all day, and don't know anyone doing that ). 10 minutes of web browsing will use more power even on a white background than 30 minutes of full black home screen.
i have this problem(maybe common in amoled devices) if i take gray pitchure and put it on background there is distorsion in grey. like brighter and darker stripes(but you need to look it realy good) for exsample download program screen helper lite and tell me do you see stripes on main gray program screen.
There is a thread going for so long,
http://forum.xda-developers.com/showthread.php?t=1079444
Regards.
I think that he meant this:
http://forum.xda-developers.com/showthread.php?t=1075364&highlight=banding
http://forum.xda-developers.com/showthread.php?t=1121840&highlight=banding
I dont think he is refering to both yellowish screens or banding.
I'm having this issue too. It doesnt show itself unless the screen brightness is turned down, and especially an grey background. There will be faint large vertical stripes. It is as if the backlighting is uneven. Increase the brightness and it'll go away.
Seeing that i do not have the yellowish screen problem, no stuck/dead pixels and no bluish tint problem, im very reluctant to send this phone back for a replacement due to this problem. Its something that i can live with.
Hi 2 All,
I have galaxy s4 installed offical 4.4.2, when i open setting or task manager in very dark place, i saw abnormal brightness in background.
i thinks it should be black as it is amoled.
is it normal or serious?
is it sign of screen burn?
sutharmukesh88 said:
Hi 2 All,
I have galaxy s4 installed offical 4.4.2, when i open setting or task manager in very dark place, i saw abnormal brightness in background.
i thinks it should be black as it is amoled.
is it normal or serious?
is it sign of screen burn?
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Open a completely black image. Download a solid black JPG from google as your test. Do the same thing with a completely white image.
Look at those images in full screen mode.
If there is burn in (which CAN happen on an LED screen, though it's actually pixel fading rather than burn in) you should be able to notice it with this test.
If you see fading in the white image, or general non-uniformity in the brightness, it's a sign of fading. (burn in)
If you see a ghost image in the black image, then something is wrong. It means the screen is lighting up when it shouldn't be.
You should not be able to see a residual image on a black screen like you used to with an old CRT computer monitor. The burn is doesn't work that way. What happens is the pixels lose some of their brightness over time. It's subtle, and if the screen is fading uniformly you probably won't notice. But when 1 spot isn't fading, you notice it quickly. This is most commonly seen with the status bar. If it's always black and the area right beneath it is always colored, then the black status bar wont' fade and the rest of the screen will.
Skipjacks said:
Open a completely black image. Download a solid black JPG from google as your test. Do the same thing with a completely white image.
Look at those images in full screen mode.
If there is burn in (which CAN happen on an LED screen, though it's actually pixel fading rather than burn in) you should be able to notice it with this test.
If you see fading in the white image, or general non-uniformity in the brightness, it's a sign of fading. (burn in)
If you see a ghost image in the black image, then something is wrong. It means the screen is lighting up when it shouldn't be.
You should not be able to see a residual image on a black screen like you used to with an old CRT computer monitor. The burn is doesn't work that way. What happens is the pixels lose some of their brightness over time. It's subtle, and if the screen is fading uniformly you probably won't notice. But when 1 spot isn't fading, you notice it quickly. This is most commonly seen with the status bar. If it's always black and the area right beneath it is always colored, then the black status bar wont' fade and the rest of the screen will.
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Thanks Sir,
actually it was lcd problem
Hi there !
Just call me a noob - but I don't understand a feature of that "Ultra power saving mode". It's the black and white display.
If we dare to ignore the special features of a pentile matrix, it comes down to a pixel consisting of three subpixels: Red, Green, Blue (RGB).
To display greyscales of the color "white" , we need ALL THREE subpixels illuminated: [•••]
For displaying the colors "red", "green" or "blue" we'd need just ONE subpixel illuminated: [•] or [•] or [•]
Clear so far ? - Well.
AMOLED displays control each subpixel directly - many subpixels illuminated = high energy drain, few subpixels illuminated = low energy drain.
So is there any sound reason for choosing a display color (grey) which always needs ALL subpixels illuminated, thus causing three times the battery drain a red, green or blue display would cause ?
Do I overlook something ?
AMOLED display is just multiple lights producing images. The reason the ultra power saving mode is black and white is because AMOLED display will turn off the light in the subpixels to produce the black color.
Chefproll said:
Hi there !
Just call me a noob - but I don't understand a feature of that "Ultra power saving mode". It's the black and white display.
If we dare to ignore the special features of a pentile matrix, it comes down to a pixel consisting of three subpixels: Red, Green, Blue (RGB).
To display greyscales of the color "white" , we need ALL THREE subpixels illuminated: [•••]
For displaying the colors "red", "green" or "blue" we'd need just ONE subpixel illuminated: [•] or [•] or [•]
Clear so far ? - Well.
AMOLED displays control each subpixel directly - many subpixels illuminated = high energy drain, few subpixels illuminated = low energy drain.
So is there any sound reason for choosing a display color (grey) which always needs ALL subpixels illuminated, thus causing three times the battery drain a red, green or blue display would cause ?
Do I overlook something ?
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U r right ...
So... Instead of white pixel there should be one of 3 main colors ( red blue green ) in order to minimize the power consumption .
Using white pixel makes no sense for AMOLED displays ...
does having a red blue or green tinted display make any sense to you ? that is why.
Found this information, maybe it is useful:
An AMOLED doesn't have a backlight at all.
Instead, each little sub-pixel is like a tiny red, blue, or green colored light.
If the screen is instructed to display black, it doesn't need to block any light, it simply doesn't light up any of the little colored sub-pixels.
So theoretically, black pixels save you a lot of power because those pixels can be turned completely off.
However, people sometimes make the mistake of thinking this is a function of brightness—that dark colors like gray are similarly efficient.
Source: http://www.greenbot.com/article/283...interface-really-save-on-amoled-displays.html
Kind regards, Stefan.
zurkx said:
does having a red blue or green tinted display make any sense to you ? that is why.
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Did you understand the purpose of an energy saving feature ? - I'll tell you. It's for saving energy.
Not for giving you a pretty sight.
Basic information (I thought everybody knew that): AMOLED indeed is like millions of single LEDs. The more illuminate, the more power you need.
Black screen: NO energy consumption. White screen: Highest energy consumption (because white light consists of red, green and blue light). Red, blue or green screen: 1/3 energy consumption, because just one out of each three subpixel LEDs is lit, thus just one out of three subpixel LEDs consumes energy.
So you need ONE LED for displaying a red, blue or green pixel. But you need THREE LEDs for displaying a white or grey pixel, so it's three times the power consumption.
Now again: It's an energy saving feature. With a green, red or blue screen, energy consumption would be 33 %. But with a grey screen, energy consumption is 100 %.
So where's the sense ?
you're incorrectly making the assumption that an active subpixel always draws full power.
if a subpixel is used to display #808080(which should be a very average grey) it should use around 50% of what it uses when used for displaying #FFFFFF(white)
I don't know how power consumption scales compared to brightness, but using multiple subpixels at 25-40% instead of 1 subpixel at 100% would save a lot of power if power consumption scales with an upward curve as brightness increases.
I don't know the exact characteristics of OLEDs or the effect that pentile has on battery usage so I can't exactly tell why it would drain less in B&W than in color, but grey definitely drains less power than white.
1 interesting thing I just found out:
while I've had several OLED devices, the Note 4 is actually the only one I've ever seen that turns off subpixels to display pure black(#000000)
other devices keep subpixels at their lowest active setting, resulting in a faint green/grey glow.(effectively #010101-#101010, as the lowest setting can vary in brightness between different subpixels)
a downside to this is that black causes ghosting, as it takes a subpixel significantly more time to wake up than to increase brightness.
EDIT: I just did some calculations and comparisons, although this example specifically applies to RGB screens you'd notice a similar effect in RGBG screens.
to create the B&W equivalent of a single colored subpixel at 100% brightness you'd need 3 subpixels to be at only 28%.
even if power consumption is linear to brightness it would still mean a drop in display power consumption of 16%
no its for pretending to save energy not to actually save it. it looks like its an eink screen in that mode so people are happy. thats the sense.
Possibly another reason for choosing black and white instead black and green or other colors to have subpixels "age" at similar rate instead one color loosing brightness at faster rate than others.
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