As a prospective 27" i7 iMac owner, I've been following the thread on the yellow tinge issues for awhile now. Hoping that Apple had addressed the issue, I finally took the plunge and ordered my system on 1/20 and just got my shipping notification yesterday.
As I wait for it to arrive, I wanted to share some thoughts that came to mind after I read this
review of a Samsung LED television a few days ago:
Getting the LED white light to travel from the edges to behind the LCD panel requires an optical wave guide that twists the light 90 degrees. This is no easy feat to perfect and Samsung hasnt managed to completely nail it: screen uniformity wasnt perfect when viewing a full white screen test pattern. On rare occasions, when viewing content with white areas at the top or bottom edge or a blue sky, this non-uniformity gave the screen edge a schmutzy (dirty) appearance.
If this is an issue for a large TV then it may also be a problem for the iMac's 27-inch display. This got me thinking about what a Gizmodo reader mentioned last week in this
article:
I now am fairly certain that the yellowing of the display is a manufacturing defect involving the distance between a layer of material used to diffuse the LED backlight and the LCD panel. To show a perfectly even color, this light scattering panel has to be absolutely flat and free of any warping, kinking, or thickness defects. It is this layer that I believe is at fault, and causes the color to drift and give the perception of yellow stripes, fields, and corners.
This would be absolutely consistent with the reports of horizontal and vertical stripes (a vertical or horizontal kink) or corners (a bad tuck). I believe these defects may not appear in the factory. Rather, with the rough handling the monitors receive when shipped this layer gets knocked out of alignment.
Something to think about with the iMac is that it's shipping weight and bulk is a whole lot heavier than a typical monitor and the LCD panel is wedged between and fixed to metal, glass and the logic board and components behind it. Now I've seen how the FedEx and UPS guys handle packages coming to my house and office...factor in a trip all the way from Shanghai for a mega parcel and I'm sure there's a lot rough handling that the iMac has to endure. I think it's entirely possible that the backlight diffuser is getting warped in transit, perhaps at certain contact points like the lower corners. Heat from the system behind might make the problem appear worse over time as some users have commented.
If this is the case, then it would explain why some folks are getting their 5th and 6th yellow-tinged iMacs whereas others are fine. Apple could do all the QA in the world on the factory floor but it wouldn't help if the problem occurs during shipment.
Bottom line is that this would be a serious product design flaw which would take alot longer than a few weeks to fix and retool for. The only other solution would be for Apple to replace the LCD panels for those machines on which the diffuser was warped during shipment, which appears to be the direction they are heading.
Anyway, here's hoping that the FedEx takes good care of my package!
