Hi,
actually I do see the yellow tint. But even though I would prefer a screen with a cold/blue white I just don't think the yellow tint (warm temperature) is a display issue/faulty display. I will try to explain why I think in that way. 🙂
I checked both iPhone 5S my gf and I own. Both have no scan lines but they do have slight yellow screens. The uniformity is fine which means the whole display has the same slight yellow tint. I read about some iPad screens which are yellow on the left side and bluish on the right. This is not the case on my iPhones. My iPhones are also not very yellow, but under certain circumstances it's visible. First of all it depends on the ambient light. If I'm outside in the sunlight there is absolutely no yellowish screen visible. The colors are strong and pop out. The yellow is visible mostly when there is low light and also with some artificial lights but even then mostly just if I looked at another display (with cold temperature) before. The whole thing with the yellow screen IMO is a topic about color temeprature in the end.
First I compared my iPhones to different electronic devices, I wanna share shortly my conclusion with you.
- the two 5S were identical
- I compared two iPhone 5, one was even more yellow than the 5S and one had the very bright blueish white (cold color temperature) you described
- the Motorola Moto G had also the very bright blueish white (cold color temperature) and therefore made the 5S look yellow
- the Nexus 7 was very similar to the 5S
- the iPad Air had a colder color temperature than the 5S but not as cold as one iPhone 5 and the Moto G
- the iPhone 4 had a similar screen as the 5S but was hard to compare since the colors always look less vivid on the iPhone 4
- the iMac from 2008 had a much warmer (yellower) screen then the 5S and the 2011 iMac had a slighty warmer screen than the 5S
If I look at all these screens then the 5S is avarege if it comes to color temeprature. Obvisouly you can trick the brain by first looking at a colder screen which makes the 5S look yellow. But this also works the other way around, if you look at a warmer screen first, the 5S looks colder and you will think the whites are very bright and just perfect.
The most interesting comparison was my Sony LCD TV though. IMO comparing the 5S to a TV shows exactely why the yellow display is in the end the better calibrated display and the blueish one is the wrong calibrated (better calibrated doesn't mean you actually have to like it more, just that it is the way it's supposed to).
On the TV there is an option to change color temperature. Mine has cold/neutral/warm 1/warm 2. Cold and neutral had a (much) bluer white than the 5S and therefore looking at the display and then looking at the 5S made the 5S look yellow again. Warm1 was more or less the same as the 5S and Warm2 was much(!) warmer than the 5S which made the 5S again look very blueish with "perfect" whites.
Now the interesting thing is, warm2 (and not cold or neutral) is the correct color temperature! You can check every professional calibration for like every TV out there, the warmest setting usually is the correct one. The point is the brain gets tricked by the cold temperature. Almost all the people will think the neutral temeprature is the best one and that's why almost every TV has the neutral temperature as the standard setting. Actually I'm no different than these people, I also like the neutral temeprature, but believe me the neutral or cold temeprature is a wrongly calibrated display.
My guess is, your brain is used to look at displays with cold temperatures and I really do understand why you prefer these displays because so do I. But that doesn't mean the yellow 5S screen is a defect. Actually if I compare it with my TV settings it still isn't warm enough for a correct calibration (thank god Apple didn't make it more yellow though!). Try it out with your TV. Change the color setting to Warm2 (or whatever the name for the warmest setting on your TV is). I'm pretty sure it will make your 5S look not yellow at all. If your 5S even then still looks more yellow than the TV, I guess you really have a bad display. 🙂
My final conclusion is that yellow or not yellow, all these displays are fine (if they don't have the scan lines). The problem is that Apple doesn't make the effort to calibrate them in the same way (and also doesn't offer an option in the settings to change color temperature). Even two of exactely the same panels have slight differences and need to be calibrated slightly different to get the same result, now imagine panels from different brands. That is the reason why some displays are more yellow and others are bluer. In the end it's a question of personal taste but neither the blue nor the yellow display is a defect and therefore IMO the 5S displays without scan lines but with the slightly yellow screens are perfect from the tecnical point.