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General Is The Screen Really All That Big?

Discussion in 'Android Devices' started by RichSz, May 11, 2012.

  1. RichSz

    RichSz Not Entitled
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    I've seen a bunch folks commenting about the GNex battery drain saying something like "what do you expect with such a huge screen?" I've given this some thought and I'm not convinced that's accurate. Let me explain.

    It has a 4.65" AMOLED screen which is larger than any phone besides the Galaxy Note. This is a fact. AMOLED has an interesting property in that it only uses power for pixels which are lit. This differs from standard LCD screens where they uniformly use power regardless of what is being displayed. This is important to my point.

    On the GNex, the darker the screen is, the less power it's using. Also, the less pixels lit, the less power it's using. Here comes the controversial part.

    When you "remove" the screen area taken up by the soft buttons, you are left with 4.33". That's the same as the Droid X. Looking at the button area, you may notice the buttons illuminate very few pixels relative to the area and the pixels which are lit are not at full intensity but are grey. I assert this area of the screen uses very little power. Therefore, relative to the rest of the screen, the button area uses very little power and has little impact on battery life. This makes a comparison with similarly sized phones nearly apples to apples.

    Comparing to the Droid X, which I used to get 2 days of battery with, if the screen on the GNex is the main culprit of battery usage, per the built-in stats, then something is wrong if you keep your screen relatively dark.

    For example, I keep my screen at a brightness of 33% or less and choose dark backgrounds/themes where possible, yet my battery life is nowhere near that of my Droid X with the main drain identified as the screen.

    I suggest that the screen is somehow very inefficient if it is using so much more power than a "same sized" LCD screen such as the Droid X. So I can't just explain away the power drain based on the "huge" screen the Gnex has. Something else is wrong.

    I realize LTE gulps battery but unless I'm in a very weak area where the phone struggles to keep an LTE connection, the screen is almost always the biggest drain.


    Thoughts?
     

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  2. pool_shark

    pool_shark Android Expert
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    Two things:
    1) It's also dual core, the DX is not.
    2) When watching video, the soft buttons disappear and the screen expands.
     
  3. SharpBarb

    SharpBarb Member
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    Not when you consider that the bottom 3/8" of the screen is usually taken up by the soft buttons. Also, When the buttons hide (like for video), there is noticible image retention when the soft buttons are.
     
  4. DannyJSlone

    DannyJSlone Android Enthusiast
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    Mine is rooted with a custom rom so I don't have any on screen buttons. I love the full screen. I came from and original incredible so the screen is huge to me and I love it.
     
  5. binary visions

    binary visions Android Expert
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    AMOLED screens do not use zero power on pixels that aren't lit.

    If you turn off the lights, a completely black screen is not exactly completely black. It's dark, but not black - so by the very definition, it must be using power.

    Without being an expert on the screen tech, I wouldn't like to speculate on how much the power differential is. It's certainly less because of the nature of the technology, but it's not zero.

    edit: also, the screens are less efficient than LCD when displaying white pixels (i.e. they draw more power when displaying bright colors).
     
  6. jbdan

    jbdan Extreme Android User
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    OP how long have you had your DroidX and is it rooted? How much longer has the DroidX been out than the GN? Did your DroidX get that kind of battery life in it's infancy? You can probably see where I'm going with this.

    I'm extremely happy with the battery life of my rooted GN and stock battery. Better than the Eris, Inc, and Droid Bionic I've previously had.
     
  7. colchiro

    colchiro Extreme Android User
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    The SGN has a lot more pixels to manage and the GPU is much faster.

    DX: 480 x 854 = 409,920 pixels
    GN: 1280 x 720 = 921,600 (2.25 times more)
     
  8. Tim K

    Tim K Android Expert
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    This....

    and that.
     
  9. TheyCallMeBT

    TheyCallMeBT Android Enthusiast
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    And this again. lol. Yeah, it'd be nice if the battery were a bit better. But it's a heck of a beauty, that screen.
     
  10. Bramsy

    Bramsy Android Expert
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    The DX have LTE?

    That's what kills my battery... the abuse of my 'unlimited' 4G
     
  11. wrecklass

    wrecklass Well-Known Member
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    Actually if you do a bit of research you will find that the AMOLED screen of the same resolution as a Standard TFT backlit display will use less power on average.

    The TFT back light is always on, and despite the fact that the AMOLED uses more power for a pure white display the average image uses less than 50% white pixels.

    With a predominantly dark/black screen the AMOLED display uses far less power. So use of dark wallpapers, dark themes in Apps, etc. power consumption will be best on the Gnex.
     
    batkinson001 likes this.
  12. RichSz

    RichSz Not Entitled
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    This. And that's why I said I use themes/wallpaper which are as dark as I can make them. I'm not saying there is some conspiracy or everyone is wrong. I just don't think the screen's battery usage can be excused by saying it's a big screen.


    colchiro, the GNex absolutely has more pixels but shouldn't that mean each is smaller and would therefore use less power? Would a square inch of white pixels on a 300dpi screen use more power than a square inch of white pixels on a 200dpi screen? 90,000 lit pixels vs. 40,000 but still outputting the same amount of light.


    Bramsy, agreed the DX did not have LTE which is a battery killer, but the system almost always reports the screen as the main battery drain. Except in the morning when the 13% drain I often see clearly has nothing to do with the screen.


    jbdan, I had my rooted DX for a year and a half and it always had much better battery life than my GNex. I'd love to think a future update will improve this but am not that hopeful. I wish I knew what I'm doing "wrong" when I read of others getting fantastic or at least acceptable battery life. No FB, G+ disabled. Rooted but stock. Maybe I need to start exploring other ROMs.


    binary, perhaps black != 0 battery usage (which is weird to me because a black LED should be off), and I agree white is worse which is why I keep it dark. For example, while waiting for a car repair I used Mantano reader in night mode (black background, white text) with the brightness turned way down (dark grey lettering in the end) and still ate battery such that I went through a considerable amount of battery in 2 hours. Don't remember the exact drain, so I can't give an objective report. Maybe a future update will make black = unpowered pixels?


    Just so you folks know, I'm not being argumentative. This is something which, even after your answers, still doesn't really make sense to me. For me, this is a discussion, not an argument. No way to win or lose. :)
     
  13. binary visions

    binary visions Android Expert
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    Exactly. Of the same resolution. Those are the key words.

    RichSz, the pixels being smaller doesn't mean they consume a linearly smaller amount of power (i.e. 1/2 the size doesn't mean 1/2 the power consumption).

    The new iPad draws about double the power for the display, despite it being the same size as the iPad 2 (and thus no additional backlight needed). It packs in 3x the amount of pixels - so again there's not a linear correlation between pixel count and battery consumption, but it's still a significant increase. Different screen technology, of course, but it shows that the colored pixel itself isn't the only thing drawing power - there are electronics needed to activate and control that pixel, and those controlling electronics don't scale down well on their power consumption.

    Additionally, you have to use significant amount more processing power to move those pixels around.

    Couple other thoughts:

    - even though the screen is black around the button area, there are still the touchscreen electronics that remain active, unlike hard buttons.

    - the inefficiency of AMOLED for white pixels is significant, something on the order of 4-5x less efficient. So if a screen is even 30% white pixels, it will be using more battery than a traditional LCD.

    This is all leaving aside LTE, of course, which is a huge battery killer... but is not the subject we're discussing.
     
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