February 8th. Apple has initiated steps to rectify the Yellow Screens with a one-time only screen replacement service. The repair/replacement service are quoted to take 3-5 days. Theory on the cause, and an Apple memo via Gizmodo. Macworld article Test Instructions: Go to the link below with the height and width of your window maximized, http://tapplox.com/imac-led.html While focussing your eyes on the grey bars at the bottom Resize the height of your browser window so that the grey boxes are almost touching Resize the browser back to full size Repeat steps 1-3 several times. Do the test while you are looking directly at the screen, do not tilt your screen up or down. Align your eyes perpendicular to the screen. Note: Your screen may have the yellow tinge on a corner as opposed to the entire bottom. The following links might be useful to help you look for them. Top vs Bottom grey bars (single color) Left vs Right grey bars Confirm whether or not the two bars look indistinguishable in color during the entire test. There maybe slight variability in LCDs, but there should not be a significant color shift. Most of the displays with the issue have a noticeable much warmer (yellowing) tone towards 1/3 bottom of the screen, as illustrated in the photos below: Tip: The grey bars will look identical in color when they are close together (near the top of the screen). The yellowing issue starts from the middle towards the bottom of the screen. Tip: The issue will appear to be more severe and more apparent in dark room conditions (preferably with all lights off). It will also be much more apparent if you lower the brightness. Try doing both if you are not sure whether your display has the problem. Do try to play with ambient lighting conditions, sometimes in a very bright environment the yellow tinge is much more subtle. Warning: Do Not Tilt the Angle. If you do tilt the screen upwards, the yellow will fade — BUT as this happens, the top of the screen turns Purple, which will be more difficult to notice in grey. Anyway, nobody should be using their iMac in such a way. If you are doing the test, try to align your eyes normally. Note: Other forms of color uniformity issues maybe present. There are reports of honeycomb yellowing patterns, yellow band that run horizontally, yellow band that run vertically, and or significant splotches of yellowing towards the lower left or right corner. These maybe developed from the same problem documented here. Carefully observe the differences. While there are slight variability for LCDs, there should not be a significant color shift/cast. The color uniformity for LED IPS panels should be very acceptable. ——————————————————————————————— After you have done the test, please vote in the poll. ——————————————————————————————— Please keep in mind that this test was designed to make the "yellow tint" easier to spot. Making an unacceptable display easily identifiable. If you can't really tell after the test, chances are it is probably an acceptable display. If the display appears to be highly acceptable to you (in regards to color uniformity), though it might have a very mild color shift, there really isn't much to worry about so long as it does not affect your day to day usage. But do keep in mind that while your display might look acceptable in your eyes, it might not be the same for some others. This poll applies to new iMacs only. Do not vote otherwise. If your display shows identical colors after doing the test several times, it means that your display has no such issue. If you could list your week number for your iMac here it will help Apple track down units. If your display has other related issues, you can describe it below. Alternative Tests 1. Open a finder window and expand it to the full screen. Use the detail view with 'White & Blue' separators. If you have the yellow tinge it should be very easy to see the uneven color uniformity. 2. You can try using an app window's grey color (Finder, Safari, Mail, etc). Simply observe the color of the window while it is to near the top and then dragging it down towards the bottom. If your display is affected you'll see the grey shift to a warmer (yellow) tone. 3. Alternatively you can set the background as a white or grey wallpaper. Personally I can spot the yellow with the default purple Snow Leopard Wallpaper, but not everyone's eyes are trained to spot the difference. Due to the varying degrees of severity of the issue, it might be more or less difficult to tell. Helpful and Diagnostic Information: 1. Yellow Tinge is a color uniformity issue for both 21.5" and 27" iMacs 2. Not everyone have the issue, but it is extremely common. 3. There's a difference in severity of yellowing. Some reports cite that yellowing worsens over time while there are some that said it had remained the same. 4. The issue is NOT a backlight leak nor backlight inconsistency. This is a color inconsistency issue. If you desaturate photos taken of the yellow tinged display, you will see even backlighting. 5. It is not GPU specific. Reported issue seen on Nvidia 9400M, ATI HD4670, ATI HD4850. 6. It is not CPU specific. Seen on Core 2 Duo, Core i5, Core i7. 7. It does not affect External Displays, only present on the iMac 21.5/27 display. 8. Also occurs in Windows running in Bootcamp, so it is very likely a hardware defect. 9. PRAM reset does not help. Reinstallation does not help. 10. Issue remains regardless of brightness level. 11. Issue remains regardless if display is near speakers / magnets. 12. Issue remains regardless of viewing angle. Looking directly, up or down or from the side. Watch for it carefully. 13. Some displays may have more yellowing on the left, center or the right side of the affected area (from mid towards the bottom). 14. Some of Apple's 24" LED Cinema Display also exhibit this issue. 15. First batch of refurbished 21.5" iMacs also exhibit the issue. 16. This is not a discoloration of the glass itself. 17. The firmware update from December 21st 2009 does not fix the issue. 18. Previous generation 24" iMac's yellow tint issue, link, is similar but goes horizontally across the screen. 19. This may not be a LED problem. 20. The firmware update from February 2010 does not fix the issue. Breakdown of reports for Week/Batches To find out about your unit's Week/Batch number, look at your serial number. W8947XXXX — translates to Week 47 Week 39: One 27" with extremely subtle yellow towards the very bottom. And one 21.5" that is yellow-free. Week 40: Not all are yellow-free. Week 41: Not all are yellow-free, but are mostly good. Week 42: Normal display reported. Week 43: Unknown. Week 44: Yellow Tinge and Non Yellow Tinge cases reported. Week 45, 46, 47: A lot of these exhibit this issue. They are the more pronounced than other weeks. Week 48: There have been a few real Yellow free screens. But still many with the issue. Week 49-51: Many reports of Yellow Tinge, some more subtle than previous weeks, some worst (especially week 51). More recent week 51 units reported without the issue (but not confirmed by tests). Week 52-53: Still many reports of yellow tinge.. Week 02-03: Might have been less reports of the problem, but still many. Refurbs: First batch of 21.5" iMacs have the issue. No data on newer batches. Some reports cite that they worsen overtime. Some more severe than others—especially after a full day of use. Except for exceptional cases of a perfect display, like some of the week 41 batch. Evidence of week 40/41 yellow free displays. Possible Cause Apple is out of 27" Display (parts) as of February 3rd, 2010 Apple's Memo Latest Apple's Official Response(s) Links to other related discussions Yellow Tinge at Apple Support Discussions 27" Yellow Tinge thread Photos of Yellow Tinge thread Yellow Tinge at imac.squeaked.com Gizmodo 1st article Gizmodo 2nd article Theory on the cause, and an Apple memo via Gizmodo Macworld article Wallstreet Journal - report on iMac delays. Yellow Tinge Photos Yellow (left) vs Yellow-free (right) 27" iMacs. Photo courtesy of Mitch Aunger Greybars 100% brightness. Yellow tinge bottom right (left), Yellow vertical stripe center (right). Photo courtesy of knewsom Finder (details view) test at 50% brightness. Yellow tinge bottom right(left), Yellow vertical stripe center (right). Photo courtesy of knewsom Finder (details view) test at 100% brightness. Yellow tinge bottom right (left), Yellow vertical stripe center (right). Note carefully that, when compared to 50% brightness in the photo above, higher brightness levels tend to hide the yellowing slightly. Photo courtesy of knewsom Non-Yellow uniform screen. Courtesy of robotkiller. Yellow 1/3 Bottomon with White. Courtesy of Big iMac.