Previous 1 49 50 51 52 53 Next 2,377 Replies Latest reply: Apr 13, 2016 2:01 PM by Gurm42 Go to original post Branched to a new discussion.
  • rohanzsta Level 1 Level 1

    Anyone know where I can buy a 27' Apple Cinema Display w/CCFL backlight made in 2010/2009 ?


    Also, are we in the clear if the screen spec says "Display Type: TFT LCD" ?

  • Dave Nikkel Level 1 Level 1

    You've got a few options:


    1) Check your local for sale boards (Craig's, Kijijii, ...).  If you don't see anything listed, it never hurts to post a "wanted" ad, it might prod someone who has one sitting around not being used.


    2) Check your local Apple resellers and see if any offer used equipment (likely trade-ins) for sale.  We have several here in Ottawa (The Mac Group, Carbon Computing).


    Good luck!

  • Gurm42 Level 1 Level 1

    I spent all weekend recovering from severe eyestrain, this is getting pretty old I have to say. Not sure if it's the lights, the monitors, the driving I've been doing lately but it's ridiculous.

  • logoo88 Level 1 Level 1

    Hi everybody, some news.


    It's probably one of my last posts here. I tried MBP for a week, then MBA. MBA is less harsh for the eyes because it doesn't have those "powerfull" colors MBP has. They seem a bit washed out and that's better.

    I really love both computers and I'm so sad I have to give up.

    I don't want to damage my view just for a great laptop.


    But Apple's new screens have something special. Everyone around me think I'm crazy but I can see it!

    Their screen look the same way whites appear under "black light" of dancing floors. I have the same feeling.


    I spend the whole month reading on the internet and doing experiencies... to no avail. I don't know what's wrong with their screens.

    And I'm not an engineer so that's not my role after all.


    Today, my university has changed their computers screens to new LED ones. They are brighter and more colorful but have not the weird effect Apple ones have.

    If I were you, I would not (like I did) try to change screen temperature, fonts, buying color filters and everything else. You're loosing  your precious time.


    Otherwise, I can tell you that Apple screens DO flicker (probably because of PWM). I did the test with my camera with a 1 sec opening time. (But I can't see the strobe effect like on my CCFL).

    But all my screens flicker, the CCFL ones , my 3GS LED probably does too. If you want I can upload the photos I took?



    What I would really like to know is (and I pray someone to answer it)

    - Does a Macbook/imac with windows 7 hurt?

    - Does a mac mini with a non problematic screen hurt?

    - Any definitive sight damage to report?


    That will tell if the problem is the hardware, the software of both of them.



  • CoreLinker Level 1 Level 1

    "Otherwise, I can tell you that Apple screens DO flicker (probably because of PWM). I did the test with my camera with a 1 sec opening time."


    *sigh* And what did you find out? How could such a long exposure time tell you anything more meaningful about flicker?


    The backlight does not flicker, it looks from what you're saying that the panel does. It might be from the panel itself, or through the input channel (software/drivers etc.). It can be dithering or pixel walk or something else IDK. The lagom tests seem to be pretty definitive ways to detect both.


    Sorry if I sound kind of harsh, your post is good, it's just that the PWM claim about Apple displays has been done to death. There is no hardware manufacturer who seems to care or is aware about PWM more than Apple. They have been PWM free for a couple years.

  • mojarvinen Level 1 Level 1

    I can confirm that HP ZR2740w version 2 with the new less agressive anti glare does not flicker and does not cause eye strain.


    So, I can confirm that the problem is the PWM flicker and nothing else. Case closed.

  • CoreLinker Level 1 Level 1

    Not so fast Mr. Case Closed! We have yet to see any proof about the extremely easily detectable PWM being utilized in newer Apple displays.


    If there is any way to mask PWM and I bet there isn't, why would Apple even bother to mask it? Look at the previous posts (even just the recent ones) and you'll see that the PWM theory doesn't hold water. I am sensitive to PWM, I would know.

  • logoo88 Level 1 Level 1

    I trust you, I've used a test I found on a website but I have not so much knowledge about it, I admitt it.

    Furthermore, lagom tests don't show any flickering as far as I'm concerned.

    But is this test able to reveal a high frequency  flickering? (Still problematic because of the harsh transitions between on/off)


    I will try to test windows on it via bootcamp during the week..

  • mojarvinen Level 1 Level 1

    The pixel walk test flickers only at about 30 Hz (the explanation on If one would be sensitive to the pixel walk flicker, then one would be most likely sensitive to cinema 24 Hz flicker. I think it needs a harsh LED flicker at about 180 Hz or so, to cause problems.


    This is what I think at the moment. What comes to the Apple displays, I tested the iPad 2 display and it does not have PWM, yet it does give me some slight eye strain. So that might be due to DPI and the fact of looking at a slightly flickering grid at a close distance, but it's nowhere near the strain I get from 180 Hz LED backlight flicker.

  • StefanD13 Level 1 Level 1

    I thought to let you know my current status regarding the infamous eye strain... So:


    - I get eye strain from PWM monitors, no matter if LED or CCFL (LED is worse)

    - Provided that PWM is not present, I get as well eye strain from:

         - Win7 via DVI cable (changing font or font subpixel rendering or non-native resolution is not helping)

         - Snow Leopard/Lion on iMac 2009, MBP/MBA 2011 (changing font or font subpixel rendering is not helping, changing resolution not really tested)

         - iOS on iPad 2 and 3 (2 is comfortable than 3)

         - Ubuntu (11.10) via DVI cable (font/resolution change not tried)


    - Provided that PWM is not present, I don't get eye strain from:

         - WinXP (both VGA and DVI cable are OK)

         - Leopard on iMac 2009

         - Win7 via VGA cable (dind't test MacOS or iOS via VGA)

         - Ubuntu (11.10) via VGA cable

         - Android (Galaxy Tab 10.1, Galaxy Note 10.1), however I think the devices have a slight (what I call now) "rotated" PWM (LEDs not all off at once), since after some hours a certain strain was present, anyway the devices were for me usable

         - iOS on iPad1, iPhone 3GS, iPhone4

         - Win8 RT (Surface), could be rotated PWM is also there but device is even more comfortable as the Galaxy Tabs


    My current conclusions:

    - WinXP/Win8/iOS/Leopard are OK

    - Snow Leopard/Lion/Mountain Lion/Win7/Ubuntu have a misterious issue which disappears when using VGA cable

    - mobile LED backlit devices have all rotated PWM however due to different frequencies and algorithms some devices are more comfortable (iPad1 beeing best) or less comfortable (iPad3 worst) and other devices ranging in between...

    - colour temperature, font and font subpixel rendering have some influence but in my case, adjusting them is not bringing much relief


    They are not final, but since some months quite stable.

    I'm not so sure about Win8 beeing OK, since not enough testing.


    All this is just what is helping or not helping me, I do believe anyone saying it is not working for them, in the mean time I don't try to find any solutions anymore, I just want some devices I can use, I really hope people at Apple are reading this thread since I'm terribly sorry for not beeing able to use their latest products.


    Wish you all an eye strain free Christmas,


  • Eric Leung1 Level 1 Level 1

    Stefan, thank you for your very detailed information!


    Your tests on the VGA cable has effectively proved that to be an effective way in solving the mysterious flickering issue. I know what to pick when I'm going to buy my next monitor


    I have a question regarding the "rotated PWM" though. I have done the "camera swing test" on the Samsung Galaxy S3 and can confirm your claim that it's flickering, but not whole screen at the same time. However, I couldn't see the same with the Apple iOS devices.

    May I know if you have done anything to see that rotated PWM on the iOS devices?

  • CoreLinker Level 1 Level 1

    Stefan, could you tell us which PWM-free monitor were you using? I'm asking because I wonder what kind of scaler and processing the monitor has. Since analog signal is processed into digital with some method, I wonder why changing the resolution via a digital connection doesn't process the image the same way.


    And rotated PWM is a myth for now. With an AMOLED screen I guess it would be possible since every pixel is it's own light source.

  • StefanD13 Level 1 Level 1



    The monitor is an old Benq FP93E. It is PWM free only when used at 100%

    brightness, but the display is old enough not to have a high brightness.


    I don’t think rotated PWM is a myth (actually idea was imtroduced by

    someone else here in the forum). Opposite to ccfl where only 2 light bars

    are built in, in led displays there are 2 rows of leds and they can be lit

    independently as well.


    Indeed I couldn’t prove rotated PWM on Apple devices, but I’m almost sure I

    proved it on another Sony notebook.


    I used for measurement a phototransistor connected at an oscilloscope and I

    could see indeed a very slight sinus curve when directing the

    phototransistor at the edge of the screen. However I must admit I’m not an

    expert at all with this stuff...

  • Conan_BC Level 1 Level 1

    Hi Gurm,


    It has been more than a week since I started using Dell U3011 in my office. I'm happy to report that I am not experiencing any eye strain using the monitor. I use the monitor more than 8 hours per day. It is connected to my Windows 7 PC with Nvidia GTX 460 video card.


    I like the monitor a lot. When I first started using the monitor, I felt the size (30inch) a bit overwhelming.  When I had white background on the entire screen, I felt that there is too much light shining on me. Now I am used to it and it does not bother me any more. (Still, I might go for U2711 if I had another choice.)


    I was worried about the PWM even though it has the CCFL backlight. When I lower brightness and wave my hand, I can see the flickering. However, the flickering does not cause any eye strain for me. I set the brightness at 50 and contrast at 40.



  • Dovez Level 1 Level 1

    Could you, Eric, send me a screenshot in .bmp format of your Macbook Air with completely white content with the native screen resolution to so I could enlarge it and look if all white pixels look the same (or you could enlarge it and see yourself)? If some are dimmer than others, than it would be a definite sign that they are flickering. If not, then there is no conclusion I can make (I'm pretty sure all pixels will look the same, though). Also, all who can measure flicker might want to try measuring one isolated pixel instead of a row of pixels.

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