27", 21.5" iMac Owners, test your screen for yellow tint issue here

[jonwd7]

pics 98 and 99 were taken at the same time and same spot I just zoomed out a little on one of them. 97 was taking earlier in the day when the room was bright and i wasn't zooming at all

I think I was too impressed with the P1010097 to see clearly the rest.
But overall it sucks.

Tom B.

jicka,

Your screen has left me rather puzzled. It is very clearly a near-inverse of mine. In terms of bright/dark patches as well as blue-to-yellow gradients.

Mine was purchased last December.

Yours (Curves and Sat for effect)


Mine (Curves and Sat for effect)


Ours (A combination of the previous two)


Here are the normal images(mine and the combination to get under the attachment limit):
Mine (Normal)

Ours (Normal)


The only thing I did to your original image is normalize it to mine. I made the center 101x101 pixels average out to the 56-58% grey it's supposed to be based on the "medium" grey background I assume you chose, and then also with Levels I made the center 101px of the images to be gray balanced.

I also surface blurred mine to get it under 1MB.

With that said, it would be such a dream to combine both of our screens.

I was going to use a joke to open this post... something about "polar opposites" but I figured it would fall flat if nobody knew about light polarity, and these iMac screens being polarized. For example, if you wear polarized sunglasses you will be able to make the screen nearly pitch black. I can also make the screens on voice recorders and such become unreadable if I try to use the light from my screen to see them. It's quite funny actually.

With that said, I think it's possible the screens could literally be "polar opposites"? If you happened to have a pair of sunglasses you should see at what angle the screen appears to be pitch black at... But I guess to make that test scientific I'd have to have the same sunglasses to rule anything out.

Anyway, I'm just trying to search for a reason why our screens have exactly opposite traits. It's probably not anything to do with different light polarity.

If nobody spots what I see, here's a summary:

Mine
White bar across full screen, about an inch up from the bottom
White bar, centered, across half of screen, about an inch up from first white bar (it's more faint)
Two yellow "mountains", with peaks halfway though each hemisphere, they meet in a valley in the middle
Sitting in the "valley" is a darker, bluer blob in the center
Darker, bluer column through very middle

Yours
Black bar across full screen, about an inch up
Black bar centered, about half-size, inch up from the first bar (also more faint)
Two blue "mountains", meet in a valley in the middle
"Valley" is occupied by a bright yellow blob in the center
Bright column in very middle (part of the bright blob)

Not sure which I'd rather have honestly. The yellow of mine is bothersome to me, but I can't stand that dark bar on yours either.

Gosh, keep looking at the combined version and wishing it was real. *sigh*

 

[jicka]

Haha that's pretty crazy. Yours actually looks more like the first 2 that I returned. I thought that they all were only yellow on the bottom until I got this one. I really can't decide what to do I don't feel like I will get a better one if I return it. I really should have kept the first one it was darker yellow but only on the bottom left but It didn't have gray bars and I think this slight yellowing in the middle of the screen is more annoying than the darker spots on my other ones and the dark edge on this one because I notice it no matter where I put my window.

I seen some people posting in another thread that you only have a 1% chance of getting a yellow screen, that's ******** there is no way so many people would be getting multiple yellow screens if it is only a 1% chance of getting one haha.

I actually opened the second one in the apple store and the genius bar guy told me that the gray bands were just glare from the lights, I knew it was ******** but I took it home anyway cuz I didn't see any yellow but as soon as I seen it in a dim room it was pretty obvious that it was yellow. I'm probably going to return this one next weekend and if the next one is still yellow I'll give up.

 

[jicka]

It is hard for me to see, but maybe my sense of color is bad or something. Do you think I have the issue? This is a Command-Shift-4 capture of my 27" screen using the imac.squeaked.com test.

You need to take a pic with a camera, screen shots won't show anything.

 

[iamthedudeman]

Well I waited until it was pitch black outside to take some pics to get a better reading on my situation. This is a model bought today, my second one I bought one yesterday. Replacement.

Not too bad, what do you think? Maybe how far you sit plays a role,or certain angles of the LED are showing darker hues depending on temp. I don't know but on some angles this seems to be the case.

 

[iamthedudeman]

more

 

[Keysmark]

It is hard for me to see, but maybe my sense of color is bad or something. Do you think I have the issue?

Man, what is the matter with you? If you cannot see it and if you have to ask someone else if you have the issue, you do NOT have the issue.

I bet if you go to a hospital and get a full body MRI and Cat Scan
that you will find a medical condition that until that moment did not bother you and with which you previously had no issue.

ENJOY your new iMac

 

[iamthedudeman]

Now it looks like the angle has something to do with it. Makes it more or less severe. From a few feet away the pics don't look that bad.

 

[jicka]

Looks a little yellow on the bottom right to me, I would probly keep that one the yellow isn't in the middle of the screen and it isn't very dark if there is any at all.

 

[iamthedudeman]

Could lighting or angle play a role of how the LED looks. I think so. I can't really tell I have a problem unless I take a pic. Or test for it.

Look at this pic. Straight on from a few feet.

Looks white.

Now close in or change the angle the hue changes, to yellow.

 

[jicka]

If you don't notice it under normal use and don't do professional photo editing I wouldn't worry about it. I think that one looks good enough to keep even if you do have a little yellow it might be worse if you switch it.

I swear a see a little in the bottom right though. You need btom to test your pics haha he is the man

 

[TMRaven]

I wouldn't judge yellow based off angled pics. These ips displays in the iMac tend to get "glowy" and yellowish when viewed from an angle. They still retain original color, like an ips should, but they tend to get a bit off-hue.

 

[NeuroEmp]

Doesn't look that bad dudeman, i wouldn't mind that one, i would keep it if everything else is fine.

 

[ceshimm]

that one is good or acceptable to me.

 

[dwarnecke11]

It's on my netbook, it's on my 17" Dell, it's everywhere. As long as it doesn't jump out at you, keep it.

 

[JoelMarcey]

You need to take a pic with a camera, screen shots won't show anything.

Thanks. I will do that soon.

 

[iamthedudeman]

Looks a little yellow on the bottom right to me, I would probly keep that one the yellow isn't in the middle of the screen and it isn't very dark if there is any at all.

Thanks for all the input guys, I really appreciate it and was going crazy trying to see yellow or not.

I am going to keep it. And I concur there is a quite small amount of yellow hue in the lower right corner, but so little that it is hard to tell it's there.

I am convinced that temperature variations of the screen is causing the yellowing effect. The pictures I provided backs this up. Far away shots produce a uniform screen which is white. Close up shows the temp and produces a yellow hue. The phosphorus used is yellow I believe. I may be wrong on that one so if someone knows maybe they can give their input. I think that the original speculation of the diffuser being damaged makes perfect sense as it makes the LED colors produce white light. Again I may be wrong on this and not sure if that is how it works. But if it is it would make perfect sense on why these screens are being delivered like this. Maybe they leave the factory okay and are damaged in transit? On the inside.

different angles show different temps on the screen. Higher temps show higher amounts of yellowing.

I lowered my brightness and the yellowing in the corner is gone completely. I end up with a perfect screen. My screen is white again. Turn the brightness back up, and the slight yellowing returns. My imac came with the brightness turned all the way up!


http://www.led1000.com/Demonstrate.asp?ClassName=About LED Crystal&TypeID=2&


"White LEDs often use one or more phosphors. The phosphors tend to degrade with heat and age, losing efficiency and causing changes in the produced light color."

and

"High-power LEDs are susceptible to current crowding, nonhomogenous distribution of the current density over the junction. This may lead to creation of localized hot spots, which poses risk of thermal runaway. Nonhomogenities in the substrate, causing localized loss of thermal conductivity, aggravate the situation; most common ones are voids caused by incomplete soldering, or by electromigration effects and Kirkendall voiding. Thermal runaway is a common cause of LED failures.
Laser diodes may be subject to catastrophic optical damage, when the light output exceeds a critical level and causes melting of the facet.
Some materials of the plastic package tend to yellow when subjected to heat, causing partial absorption (and therefore loss of efficiency) of the affected wavelengths."

 

[Btom]

It is hard for me to see, but maybe my sense of color is bad or something. Do you think I have the issue? This is a Command-Shift-4 capture of my 27" screen using the imac.squeaked.com test.

Screen capture is always perfect, you need to take a picture with the camera.

Tom B.

 

[Btom]

.....
Gosh, keep looking at the combined version and wishing it was real. *sigh*

Your observations made me thinking: is it possible that from time to time they miss some of the inner panel layers at LG? If they put two properly, there is a "prefect" screen, if they miss one, there is an "almost perfect" screen. It would explain some of the iMacs being "perfect", and some obviously faulty.
Just a thought, in lack of better explanation.

Tom B.

 

[Jamaway]

Picture of my new 21.5" i3

It's going back Tuesday...

Thoughts?

 

[lexvo]

I'm more and more convinced that this yellow tinge has to do with some structural design problem. On the support forums of Apple, people are also reporting newer iMacs with yellow tinge. All screens will suffer from it, albeit in varying degrees: from clearly visible to almost impossible to see.

 

[iamthedudeman]

I'm more and more convinced that this yellow tinge has to do with some structural design problem. On the support forums of Apple, people are also reporting newer iMacs with yellow tinge. All screens will suffer from it, albeit in varying degrees: from clearly visible to almost impossible to see.

I agree totally. It is a flaw in the design. Judging by the link I posted and the problems that can persist all clues point to a design issue, or lack of structural integrity.

The yellowing seems to be a temperature flaw from the design of the LED light as described in the link above. It is weird that I can turn down my bright ness to 75% and all yellow tinge simply goes away, turn it back up to 100% and it reappears slightly in the lower left right corner.

 

[iamthedudeman]

Picture of my new 21.5" i3

It's going back Tuesday...

Thoughts?

As just judging by the picture alone, that looks alot worse than my screen. I it (yellowing) noticeable even under regular light? Mine is practically gone just from lowering my brightness level, no stuck pixels or dead pixels.

You might want to post some pics from further away and under normal light to gauge better.

Judging by your pictures I don't think any amount of adjusting the brightness would help.

I would take it back.

 

[Btom]

Picture of my new 21.5" i3

It's going back Tuesday...

Thoughts?

I increased contrast by a factor of 5 using Photoshop (Input levels 120 to 183) and here is the result.

Does it look to anybody like there is some corrugated paper inside the screen?

Tom B.

 

[Devie]

Just letting people know, I just received my 27" iMac and the screen looks pretty damn flawless to me, I can take photos but can only really do it from my iPhone 3G, can't find my damn camera cable.

Thought I'd throw that into the mix and give people a little hope when buying the new ones, the people who get good ones dont really say anything.

 

[mjsmke]

Thats the worst iMac screen i've seen so far. Much worse than the 3 i returned (though the first had several dead pixels too).

Just a thought.... i've always understood that LCD and LED screens' colours age over time and become more yellow. So wont the 'almost unnoticeable yellow' become much more prominent after 2-3 years of use?

Also if heat plays a big part in the yellowing issue, do you think this will cause any permanent damage as iMacs do run much hotter than other computers?