Yellow tinge from bottom to top of the screen, 27" iMac

Hi Dino,
I have done my measures with a Spyder 3 Elite (don't tell my wife it costed me extra 200€).
I must admit the 'Dino test' is less expensive. But I like technology, I can't resist. 🙂

6600 Kelvin average on top (rather uniform) and 6200 average bottom *but not uniform* (6350 left and 6100 right).
The panel passes the Dino test, I write on the Post Message form full page : no sign of yellowish.
But the gray bar test shows a slight difference Top-Bottom and a warmer bottom-right corner.

Try to borrow a colorimeter -maybe from Apple store 🙂 - and test your unit.

Here are a few evidences we have confirmed so far about the defect :

= it varies widely from one unit to another,
= early units are better (week 40-41 2009),
= it's a color shift to yellow (meaning not a LCD problem but a thermal issue with LEDs - my opinion),
= the shift is stronger in the bottom-right corner (on most units).

The color shift to yellow (color tint) is meaning a lot (starting from here my theory).

There are no white LEDs, but different ways to make white light using LEDs. The most common (and economical) way to produce white backlight is to use blue Leds (InGaN) with a yellow phosphor (YAG) on the top of it.

The combination of blue light emitted from the InGaN and yellow light from the YAG phosphor produces a light that appears white.

Among other causes, there is a color shift associated with the LED temperature; the dominant blue wavelength of the InGaN is increasing (as the intensity of the YAG ) resulting in the shift to yellow.

All this seems IMO to point on a thermal management issue, with the iMac panel.

See this article in The “Led Journal” and particularly Fig 2

http://www.ledjournal.com/images/PDFs/Online%20Issues/Articles/LEDJA08Microsemi.pdf

Cheers!
Jacques.

Jacques, thanks for all your research!
That article from xbitlabs was what I was looking for.

jacques, Don't worry. we won't tell your wife! 🙂 You really are determined! thanks for your research & expertise! But I don't need any fancy tool, to tell me there is a Color Variance on my screen. All I need is the poor man's version of the Grey Bar Test. That test does not give me the exact variation in Numbers, but my eyes can see it plain as day. One thing I find funny though. All the people who claim they have perfect screens, never post pictures. I wonder why that is. 🙂 I'm dying to see a perfect screen that is not a screen capture, aren't you? And I'm sorry to push the point again, there is no perfect screen. Not at this point in time, anyway. Now what did Apple do so different in the design of this model from the last model 24'? I tested & client's 24" iMac & his was perfect. So is this a different screen manufacturer? It's NOT the size of the Screen, as the 21.5" has the same issues. I'm waiting for the day 10 people post their perfect screen pictures of a Week 12 iMac. Am I dreaming?

Dino,

The only constant between the 21.5" and the 27" is the LED backlighting which seem to be the most obvious culprit. I have never tried the test on a 24" LED Cinima display but it would be interesting to see the result. The old iMac 24 did not have LED back lights.

I have tried testing an assortment of LCDs (24" LCD's from Dell, Samsung and LG) and none failed in the same way my iMac did. Most of them just had different shades to the gray bars. Which I would be more than happy with on the iMac. However, there were no wacky colour casts and no LED backlights 😉

Message was edited by: mrg123

What week was it made?

No change. Yellow evident. There is even a scratch on the inside of screen or the display itself. Love the keyboard.

So the backlit LED, sounds like the Culprit! Good Point!

This was a replacement display for a machine from last year. I think week 46. I was told the replacement display was from the newly "fixed" stock and had a different part number to indicate so. I think that was a load of BS. Also, the machine that I tested in the store with a colorimeter had its white point set around 7000K. I wonder if they are doing that to disguise any yellow tinge by tilting the balance toward the cool side. Just a thought.

Awaiting the arrival of my second 27" quad. Should be in end of this week.

Hi again guys,

I hate to tell you that I tried the 'Grey Bar' test on a 24" LED backlit Cinema Display in my local Apple store. It was hooked up to a Macbook. Guess what. Yellow tinge. My heart sank -I thought that was going to be a way out of this mess...

Unfortunately once I showed it to the guy in the store, he wouldn't let me see if any of the other Cinema Displays were affected. -One which had full-frame white displayed looked 'ok' but the lighting in the stores makes it harder to discern.

While I could understand the panel in the imac being of a more 'budget' I would be really unhappy shelling out £650 for a monitor with colour inconsistencies like this...

Does the Cinema Display use a similar backlight technology to the iMac ?

I'll do a little digging...

Cheers

Time to say goodbye;
I have followed the postings here and watched the 610,000 views climb on the flicker side before Apple reset the counter. I continue to sit in amazement at Apple's inability to properly manage what is a policy and customer nightmare.

When I hear such glowing comments about the Genius Bar and Applecare I am reminded that just having a relationship with these functions is only a sign of a major problem. The fact they are nice completely misses the point. Do you really want to have a NICE relationship with a fireman, parole office or a mortician. You should never need to even know the Applecare number let alone see them on a weekly basis.

Good news from the makers of Spyder 3. Their stock is up and they are thinking Apple. How many of you would have bought this now, not later, but now.

Lastly, realize I wanted to be a Apple and IMac user. I subscribed to MacLife,
MacWorld, ICreate, bought Switching to Mac and Mac OSX Snow Leoparf, bought a black Apple hat, and ordered a I7 and planned on ordering an ITouch to replace my Dell Axim. Then I realized that Apple shut down production and was refusing to both admit to and really fix these problems. I canceled my order and waited. I still wait. I have been at this for over 40 years and have also been the one having to fix much the same problems. I told my customers the truth and we both learned to live with a timely and realistic solution without an intimate relationship with the return center.

But today I bought a Gateway I5 750 and will wait till Christmas again and see what transpires then. I am still wanting an IMac but not with this much denial.

If I can offer a guess as to the Apple Corp priorties;

IPad - its new and needs all the focus it can get
ITunes - 10 billion downloads - what a money maker
IPod - the tunes have to go somewhere
IPhone applications with no real work on Apple's part - what a country
IPhone - applications have to go somewhere
OSX
ILife, IWorks, other software
Macbook Pro 13
Macbook Pro 15
Macbook Pro 17
Macbook Air
IMac 21.5
IMac 27
Mac Mini
Mac Pro
The problem is that the IMac is at the bottom of the food chain, commands a lot of resources and does not generate the margins of products above. Laptops are in and desktops are out industry wide.

Bye for now and see you at Christmas. By the way, if you are reading this feel lucky as I suspect the moderator will take it down shortly as he/she has done with similar posting in the past.

Richard, the 24" Cinema display is also LED. So are the laptops, and I can see yellow tint on my MacBook Pro.

These iMac displays were initially much worse (and many still are), so the yellow tint got a lot of attention. Now there is a bit of a yellow tint frenzy and although the problem is very real in many cases, I have no doubt that some people are returning screens that are reasonable. In a way, the grey bar test is too effective at revealing the imperfections. And once you know that the imperfection exists, your mind amplifies it. Been there, which is why I now have no 27" iMac and $2k burning a hole in my pocket.

Apple is in a bit of a pickle, because the only way to fix this (at least for people on this thread) is to build these screens to a much higher bar than is typical of a consumer monitor.

I wonder if they are doing that to disguise any yellow tinge by tilting the balance toward the cool side

mstrammd, I had the same thought when I was going through in store replacement and one of the machines we opened was noticeably blue at the top. But it isn't necessarily that they are "disguising" the problem. It may just be the result of an attempt to calibrate the display. For the more extreme examples of yellow tint calibrating the center of the screen to Apple's pure white will lower the top to a very cool temperature.

It would be interesting to know their calibration procedure and whether they have changed it at all for these iMac displays.

Just wanted to report back from my trip to the local Apple store here in Toronto (at Eaton Centre for those who know where that is).

I tested both 27" iMacs on display, four 21.5" units (there were so many all over the store so it was difficult to get around to every single one) and the lone 24" Cinema Display.

ALL had the yellow tinge. I ran the imac squeaked flash test ( http://imac.squeaked.com/test.php) and opened the browser to the Apple store's homepage on all of them and took a nice long stare at each. The 21.5 units were immediately obvious, I didn't even have to look twice. Strangely enough, the 27" units were less obvious - I found the larger display allowed for a more gradual transition from top to bottom - I could almost live with that if it didn't cost close to 2 grand for one.

The 24" display was the best of them all, but still had a pronounced patch in the bottom middle. Otherwise, most people could probably get away with using it and never noticing anything.

Still, a very disheartening trip to say the least.

Oh, and the security woman there definitely gave me the evil eye a few times, thankfully it was really busy in there so I was left unmolested as I ran riot testing units across the sales floor.

Nicely articulated from a Windows consumer. I used to be there and I have been through a number of Gateway's and Dell's. Good luck with your Gateway I5 750. The iMac issues have held me back as well but I could not conceive of heading back to Microsoft. Apple will resolve this, probably at Revision A, if not sooner. All machines develop issues and problems and when they do it is nice to have Applecare, Apple Stores, and Genius Bars. I think Apple remains committed to the Mac and to the midrange market which is the province of the iMac. Don't forget to check back in...