iMac display quality - blacklevel and banding

Discussion in 'iMac' started by blacklotus, Nov 24, 2009.

  1. blacklotus macrumors newbie

    Sep 15, 2009
    hi guys just wanted to get some input from you in regards the display quality of the imac 27". i know when it comes to colorful images this h-ips just shines but i am particularly concerned about the black levels this displays is able to show and eventual banding problems it might have...

    as it happens just came back from a small apple store nearby with the intention of buying the 27"....unfortunately I found a display related blocker... :\ it turned out that the exposed 27" had banding problems that were clearly visible when you opened (for example) a full screen terminal window with 100% opaque black background; if you did, you could see as at least that 27 imac showed very good black levels for over 3/4 from left to right of the display, but as you looked towards right the remaining 1/4 of the screen presented a mild gradient from black to grey that was particularly noticeable in the right edge and bottom-right corner of the display.

    I asked the guy about that and had (as usual) no idea of what could be going on nor if it was normal or if it could be a defective display. They had no more 27" displays to compare so once again I gave up on the purchase. I might give it a try tomorrow to another apple store to compare with another display.

    do you guys have noticed these banding issues your imacs? when showing a full black window on the display, do you see an uniform black level ? and what about the black level quality it shows, is it closer to a pure black or a mild grey like in the image below ?



    EDIT: sorry forgot to mention that this picture is meant just as an example of poor vs good black depth quality of an acer vs NEC 2490wuxi (2690?) display. it is not a picture of a imac 27" ...
  2. JimKirk macrumors 6502

    Oct 6, 2009
    It boggles the mind

    What is wrong with people like this?

    These are computer LCD displays and like all LCD displays they have issues with off angle viewing and blacks that look grey.

    LCD is backlit and will always look like that.

    If you want deep blacks you will need a plasma display.

    Seriously WTF
  3. tapplox macrumors member

    Oct 17, 2009
    I might be wrong in saying this, but since he's referring to the 27" iMac, which are equipped with LED backlighting, IPS class displays. Which translates to uniform lighting and 180 degrees of viewing angle.
  4. JimKirk macrumors 6502

    Oct 6, 2009
    IPS or no LCDs still have inferior viewing angles compared to plasma

    And those photos are not from any Imac I know.

    Do some research. LCDs, all of them, including IPS and LED backlit ones suffer from inferior viewing angles compared to a plasma display.
  5. DaSal macrumors regular

    Mar 19, 2008
    The Netherlands
    On my iMac the viewing angles are pretty good, I mean, the colors stay right from basically any angle. However, the display gets a like white shine over it, like the brightness is all turned up, from any angle except straight on. Even from a slight angle it will have the white sheen. Is that normal?
  6. zerohp macrumors member

    Mar 6, 2008
    I received my 27" i7 yesterday and tested it out in a dark living room while watching a movie. At first I was thinking my display was defective because the black's didn't seem very deep.

    I really think I was just mentally comparing it to the only other screen in the room which is a Pioneer Elite 60" Plasma. Arguably the best plasma on the market for black's.
  7. blacklotus thread starter macrumors newbie

    Sep 15, 2009
    believe me Jim, I've tried hard during the last weeks to find a display, plasma or LCD, that can replace my current s-pva dell 2407 both in terms of quality colorful image and proper black level depth which btw, mine sucks badly on the later ... problem is that for desktop sized displays plasma is not an option (im referring < 32") there are simply no displays this size that can do natively 1080p at least. so you're left only with lcd's. thing is that LED backlit displays (as oposed to edge-lit ones) are supposed to challenge plasmas in that aspect...the so called local-dimming LEDs display will eventually deliver dinamyc contrast on pair of that of Pinoeer Kuros and given the high price tag of this display, I was really looking forward to this imac 27 exclusive LG panel to be a good contender in this area too...I know it absolutely shines in color fidelity image picture quality but for me it is really important it also delivers in black depth quality as i intend to have the imac 27 also as the display for my gaming PC rig but unfortunately it does not ... or at least it did not the one i was able to check in the apple store showed some serious banding problems...that is why i was asking for your advice.

    btw...sorry i forgot to mention. that sample picture i placed was just an example of what I was referring to when talking about black depth level. it actually corresponds to a mainstream acer 24" set (i guess) vs a NEC 2490wuxi (2690?) with A/TW polarizer that shows how the former delivers poor black depth when looked at least at from a particular angle...
  8. blacklotus thread starter macrumors newbie

    Sep 15, 2009
    yikes ...whish I could have one of those plasmas on my desktop :)
  9. JimKirk macrumors 6502

    Oct 6, 2009
    I am sorry if I was a bit insulting

    It just pains me every time I see people complaining about LCD technology because they look like crap when watching movies or complaining about black levels.

    Remember that LED backlit that these monitors use are not even the same as the LED backlit TVs with local dimming.

    Those sets actually turn off the LEDs in a region that needs to be dark thus a dark black. There are side effects however because the surrounding bright areas tend to have a halo effect around them. Plasma just turns off their phosphors and has no backlight.

    LED backlighting on computer monitors do not turn off the LEDs. That is why they will look gray rather than black.

    Plasma is the closest thing to a CRT and that is about as good as it gets.

    Try looking at a plasma at any angle and it always looks good. That is why they use them in pubs ans sports bars.
  10. zerohp macrumors member

    Mar 6, 2008
    You're replacing a 2407? I've got one of those as a second display on my PC and it's nearly the worst display I have in my house. We've got a lot of them at work and they all have fairly poor color/black level.

    If you're concerned that the 27" iMac won't have a better display than a S-PVA 2407 then stop worrying. It's far better that panel.
  11. blacklotus thread starter macrumors newbie

    Sep 15, 2009
    thanks for the tip! that's really encouraging ... as that was one of my top concerns, whether and by how much would the 27" best my current 2407 in terms of black level.

    now my only concern left is that bloody banding problem i noticed yesterday... im heading now to another apple store to see if the one they have is is any better... i will let you know.
  12. blacklotus thread starter macrumors newbie

    Sep 15, 2009
    no worries... i understand this neverending discussion gets tiresome at a times :)

    didnt know about the halo effect on the local-dimming LED LCDs... that's you know if that is done on a per-pixel basis or do they just dim the light on a particular region ?

    i am guessing the 27 panel is just LED backlit then right? sometimes it is quite frustrating the lack of technical details in the apple website...for example, anyone knows which is the dynamic contrast the LG 27" panel sports? haven't been able to find that anywhere, and once again, the apple store guy proved as useful as always...

    any how, truth is that in normal light conditions, yesterday 27" display showed very good black levels in the area not affected by the banding effect... well let's see how performs the display in the other store...if they offered me a good return policy in case there are banding problems in my set i'd buy it today blind folded....
  13. jonwd7 macrumors member

    Nov 19, 2009
    The "angle shine" with darks/blacks is specific to IPS panels and the screen would need what is called an Advanced True Wide (A-TW) polarizer to overcome this. However they must be expensive as only high-end H-IPS panels come with them. The first one I can think of is an NEC LCD2490WUXi, which costs ~$1000 so imagine the cost of 27"-30" screens...

    A-TW polarizer or not, H-IPS panels still provide much better viewing angles than TN or PVA... With my current 2407WFP, at this viewing distance, each of my eyes is actually seeing different colors because the contrast and color accuracy change so drastically with such small changes in angle. Don't get me started about viewing it at oblique angles... The entire screen becomes dark.

    So don't worry about it... All Dell S-PVA panels are inferior, and even the new Dell U2410 is inferior even though it is also H-IPS, as it is smaller, matte (higher black levels, lower contrsast), and still doesn't have an A-TW polarizer.
  14. blacklotus thread starter macrumors newbie

    Sep 15, 2009
    you couldn't be more right... ! I went yesterday to two more stores to check that 27 display again...and well, I can confirm that all the 3 sets I´ve checked had exactly the same problem, which in turn corresponds with the inherent IPS panels problem you described. So well, it turned out not to be exactly a banding problem, but more of a "glow" or "shine" that appears in the areas surrounding the center of the axis your eyes are looking straight to, the further you look from that axis center, the more intense the shine is. Too bad Apple did not include that A-TW polarizer, at least for me that is annoying although I sure that it will work for most of the people... anyhow NEC has just dropped it from the newer 2x90 Wuxi2 model too, allegedly to reduce production costs in exchange for better contrast (1:800 vs 1:1000 I believe) but people seems to agree that from a display quality point of view has been an step backwards :/

    well, as a side note good news for the imac 27" are that finally an ATI 5970 has been reported to work with this display out-of-the-box ! that´s great news since the only reported cards with Displayport reported to work with the 27" imac displayport input so far were the ones from the ATI series 3xxx and 4xxx and none from the newer 5xxx ... so good news for the big expenders :) at least the 59xx seems to be working with this display but remember, the 57xx and the 58xx are NOT.

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