yellow LED screen theory...

Discussion in 'MacBook Pro' started by redrum42, Aug 7, 2007.

  1. redrum42 macrumors member

    Joined:
    Aug 6, 2007
    Location:
    England
    #1
    ...This may well be total rubbish, but I just had an idea and thought id ask your opinions of it.

    I ran my hand over my macbook pro screen and noticed that the heat from the case was making it much hotter at the bottom than the top. Indeed the heat dropped off along with the yellowing a the bottom and seemed to follow the same gradient....could the heat be causing the yellowing?

    I did some googling and found some scientific articles that confirmed that yes, white phosphor coated LED's do change color with temperature, and specifically that increasing temperature causes deterioration and color temperature shifts to the yellow spectrum.

    Now obviously the yellow tint still exists when the laptop is turned on from cold (although it seems to get worse during use, subjective?), but the theory seems to suggest that rather than the actual current temperature causing a change of color, the deterioration caused by subjecting LED's to higher temperatures causes a permanent change in their native color. If this was the case the yellowing should get worse with time, has anyone noticed this?

    I don't have any evidence that this is true but it makes sense to me. Specifically because the mbp's have aluminum cases that heat up the screens easily and other LED screens, such as samsung's own, are plastic (they share the same design surely?). It would also explain the difference between LG and Samsung screens although both have identical systems and LED's - different construction resulting in differing levels of heat insulation. Also, this might explain why the problem seems to be getting better and more subtle with newer screen but not disappearing - maybe apple has improved the heat insulation to diminish the effects. It would be interesting to find out if "perfect" screens heat up along the bottom as much.

    Any thoughts, or am I just rambling nonsense? 8)
     
  2. kolax macrumors G3

    Joined:
    Mar 20, 2007
    #2
    I don't think it is to do with heat - good theory though.

    If it was to do with heat, then there wouldn't be perfect LED displays out there - they would fall faulty too if your theory was correct?

    I've no idea what the yellow tint is caused by, I originally thought it was possibly a yellow sticker behind the screen causing accidental illumination but that seems a waste basket idea. I'd be really interested to know what the cause is, and if there is a solution.

    Don't think a dodgy DVI connection is possible either or is it?
     
  3. redrum42 thread starter macrumors member

    Joined:
    Aug 6, 2007
    Location:
    England
    #3
    Well I hate to speak for others, but I honestly don't think there are perfect displays out there, just a huge variance in the severity of this problem.

    If heat was the cause then better insulation would explain why some (newer) screens have only a slight yellow gradient. I think the illusion of perfect screens comes from people either not noticing or coming from a screen with bad yellowing and so seeing the new screen as relatively problem-free.

    Who knows, I cant come up with any other reason which would explain the variety and spread of this problem?? - you have to hope that apple techies would have picked up on any design flaws pre-production!
     
  4. kolax macrumors G3

    Joined:
    Mar 20, 2007
    #4
    Someone posted a test you could do - it was a black background with 2 white squares, one at the top of the screen and one at the bottom.

    You could instantly see if it was yellow or not. Mine, the top square is pure white, the bottom is duller, but definitely not yellow. That's because the bottom of the screens are slightly dimmer compared to the top.

    My new screen is perfect because it doesn't have any yellowing problems at all.
     
  5. redrum42 thread starter macrumors member

    Joined:
    Aug 6, 2007
    Location:
    England
    #5
    Yer, ive tried the tests....i didnt find then that helpful, however, opening front row and getting a list of artists or albums really shows it on mine...the drop from white at the top entries to dull yellow at bottom.

    Well thats interesting, i wonder if the people with new screens that talk about having a "really subtle" yellow at bottom compared to the top are really just seeing the drop in brightness and not an actual yellowing? In which case maybe apple have fixed the issue and the new screens are fine. I never knew that the screens had an inherent drop in brightness at bottom, is that common to all laptops or just mps screens?
     
  6. raxrat macrumors newbie

    Joined:
    Oct 17, 2006
    #6
    If it were heat, there should not be yellowing when you first start your MBP and it is still cold. Also, it should get worse the more you tax your computer and generate more heat. Neither happen so this is not a good theory. It remains a (annoying) mystery. :(
     
  7. kolax macrumors G3

    Joined:
    Mar 20, 2007
    #7
    Not sure how common it is with all laptop screens, but it is pretty hard to get something illuminated completely evenly.

    http://forums.macrumors.com/showthread.php?t=330015&highlight=uneven+illumination

    It isn't a huge drop in brightness, it is unnoticeable completely unless it is a background of the same colour.

    With the brightness up full it is even harder to notice, but I strain my eyes with the brightness on full - too bright!
     
  8. Smoothie macrumors 6502

    Joined:
    Jun 23, 2007
    Location:
    California
    #8
    Good point.
     

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