Slight yellow tint to 27" iMac screen

Discussion in 'iMac' started by TripleMoxy, Apr 19, 2014.

  1. TripleMoxy macrumors regular

    Joined:
    Jul 19, 2012
    Location:
    UK
    #1
    Well, I finally bought an iMac with the following spec:

    • 3.5GHz Quad-core Intel Core i7
    • 8GB RAM
    • 1TB Flash Storage
    • NVIDIA GeForce GTX 780M 4GB GDDR5

    Unfortunately, there seems to be a faint yellow gradient at the bottom of the screen. It's not as obvious as some examples I've seen from older models, but I can see that white backgrounds are less bright at the bottom than at the top.

    The effect is only slight, so I was wondering whether it was worth swapping the unit or if all the 27" screens suffer with this problem to some extent. I would hate to go through the rigmarole of having it collected and waiting for a new delivery if a perfectly even screen is an impossible ideal.
     
  2. Chippy99 macrumors 6502a

    Joined:
    Apr 28, 2012
    #2
    They are not all like it mate. But to be honest, Apple quality control is imho not what it used to be, and if you do change then there's no guarantee that you won't get one that's better. Or one that does not have other fauits instead. My (2nd) iMac leans to the left and has a sticky on/off switch. But at least the screen is OK. The first one had debris in the LCD. I didn't want to risk the 3rd one being worse, so stuck with the leaning stand and sticking on/off button.
     
  3. Seramir, Apr 19, 2014
    Last edited: Apr 19, 2014

    Seramir macrumors member

    Seramir

    Joined:
    Nov 10, 2006
    #3
    Actually, I'm afraid they are all like that. Subtle temperature, brightness or color difference between top and bottom are normal for all displays, including IPS displays. Viewing angles also intensify the problem.

    See: http://forums.macrumors.com/showthread.php?t=1651929

    I've been through 5 iMacs and they all had slight yellowing towards bottom. Only one of them was bad enough that I consider it abnormal. Of course, each iMac was exchanged for different reasons. On mine right now I can only see any color difference on gray colors and a tiny bit on white. On any other color, it is completely uniform from top to bottom.

    People who say their iMac screens are perfectly uniform may not be noticing it or avoid trying to look for it (yes, on a good display, you have to really look to see it).

    If you aren't sure whether your yellowing is abnormal, I would suggest dropping by an Apple Store or a store that carries lots of iMacs and test to see if those yours is worst than the ones in the store. If you discover they are the same as yours, then that's probably what they are all like and you shouldn't attempt bother returning/exchanging, because like you stated, you may end up with worse problems with the new one.
     
  4. TripleMoxy thread starter macrumors regular

    Joined:
    Jul 19, 2012
    Location:
    UK
    #4
    Thanks for the answers guys. I'll try out for a bit longer and make my decision. If all of them have this issue to some extent or another, I might return it and wait for a future release.

    Unbelievable that such an expensive machine can have such a poor quality screen, and I'm surprised that more people don't complain about the yellow tinting.
     
  5. WilliamG macrumors 604

    Joined:
    Mar 29, 2008
    Location:
    Seattle
    #5
    They all do it (with varying severity). You'll note if you dip your head level with the bottom of your iMac, the effect is reduced/gone.

    And it's not a poor quality screen. :)
     
  6. Seramir macrumors member

    Seramir

    Joined:
    Nov 10, 2006
    #6
    The yellow problem has existed in iMacs since 2009. I don't think a future release is going to fix the problem. Nevertheless, it has certainly diminished to a point where it's completely acceptable to consumers, but I think it won't get any better than it is at current.

    BTW, the MacBooks have this problem as well. I heard people say even the iPads.

    Try looking at other displays in comparison though. You'll notice all of them will have some amount of color difference from top to bottom of screen. I honestly think it's just a limitation of today's LCD technology.

    The iMac screen is not poor quality at all. It uses one of the best LG 27" panel, LM270WQ1-SDF1. H-IPS, 10bit (billions of colors) and 79% Adobe RGB and 100% sRGB coverage. Similar panels can be found on very high end 27" displays in the $800-$1k range.
     
  7. TripleMoxy thread starter macrumors regular

    Joined:
    Jul 19, 2012
    Location:
    UK
    #7
    Thank you again for the replies. I'll persevere with the screen for a short while and see whether I can live with the colour gradient. I'm surprised that so many graphics professionals use the iMac; the variation in colour must drive them insane.

    In all other respects, I think that this is an incredible machine, so I'd be disappointed to send it back.
     
  8. Perilla, Apr 19, 2014
    Last edited: Apr 19, 2014

    Perilla macrumors newbie

    Joined:
    Feb 5, 2014
    #8
    I went through 5 exchanges and a screen replacement. The thing that shocked me was that every single screen looked entirely different from the others. Some had horrible IR, some had severe backlighting and varying degrees of yellow tinting on different panels (none acceptable, unfortunately). And the first one I had demonstrated none of these problems, so I knew that better ones existed.

    The experience of exchanging CTOs is an absolute nightmare.

    If you bought third-party RAM, it will be past the usual 30 day return window once you get to the 4th or 5th replacement, so you might have to pay a restocking fee.

    It's an incredible machine, especially for the money. I had first purchased a nMP in January, but realized that the iMac was more than enough for me. Too bad about the displays...

    ----------

    The iMac uses an 8bit display with 16.7 million colors. It's the same LG panel that the cheapo Korean monitors use (except they use A to A- panels whereas Apple uses A+). A 10bit display would be 99% Adobe RGB, and professionals tend to want to use those instead of 8bit. The problem? I don't think Apple supports pushing 10 bit colors yet...
     
  9. Seramir, Apr 19, 2014
    Last edited: Apr 19, 2014

    Seramir macrumors member

    Seramir

    Joined:
    Nov 10, 2006
    #9
    Well, it's not really true 10bit, it's 8-bit + A-FRC to get 10bit (1.07b colors).

    You can see the stats of the LM270WQ1-SDF1 on this website: http://www.tftcentral.co.uk/articles/monitor_panel_parts.htm

    The reason I know the iMac 27" 2012-2013 uses the LM270WQ1-SDF1 panel is quick eBay search yield displays that have been pulled from these iMacs with that model number. It's still a step up from LM270WQ1-SDA1 in earlier 27" iMacs, which were 8bit only.

    Nevertheless, I don't know if OS X or the iMac is capable of actually outputting 10bit with the display. But the panel can definitely output 10bit.
     
  10. madele macrumors member

    madele

    Joined:
    Oct 31, 2013
    #10
    Help !!

    Please let me know now if I should give up and wait for the new ones or not !!
    I am on my 4th maxed out 21" iMac and they were all yellow and overly lite on the left side :(
     
  11. Chippy99, Apr 20, 2014
    Last edited: Apr 20, 2014

    Chippy99 macrumors 6502a

    Joined:
    Apr 28, 2012
    #11
    I don't agree that all screens have "Subtle temperature, brightness or color difference between top and bottom".

    However, I do agree that all screens have subtle variations all over the screen (with varying degrees of subtleness!) Perhaps I am spoilt, having been working on Eizo and NEC monitors previously, but I have never been impressed with the iMac screens. The fact that many of them do have this yellow tint is poor. I regularly calibrate my iMac with a colorimeter and thankfully, it does not have this problem - at least not to any noticeable extent.

    ----------

    I have one word for you my friend, "binning".

    The panels Eizo and NEC put in their Coloredge and Spectraview screens are much more uniform than the typical iMac panel, even if they are the same part number. (Plus they have appropriate electronics to compensate for non-uniformity, which of course the iMac does not have.) That said, they don't cost $1,000 to be fair, much more than that.

    The end result is that the typical iMac screen is pretty poor compared to a top end monitor. Incidentally, 97% of Adobe colourspace is not great either, well when you realise EIZO can cover 99% (You said 79%, but I can't believe it's THAT bad! It must be 97%, surely!??!)

    This has nothing to do with 8-bit vs 10-bit, it's down to the panel's colour response and the backlight. The bit depth determines the number of colours and therefore lack of banding, not the extent of the colourspace.
     

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