Ok, I have now tested this with my 12 Pro and with my newly arrived 12 Pro Max and can reproduce this issue 100% of the time. The issue seems worse on the Pro Max than on the normal Pro. Also, my the results of the testing leads me to believe that this is probably a software issue and not a hardware issue, since the displays can get completely black for HDR content. It seems that there is a problem in how iOS handles HDR/SDR conversion of displayed content.
With that said, here is how you can reproduce it:
It is important to test in a completely dark environment and to let your eyes adjust for 1-2min to the darkness. This is honestly the most important point for testing IMHO. (This issue is probably mostly noticeable when your in bed at night and still on your phone instead of sleeping
)
For testing you can use this site:
https://www.lightbleedtest.com -> then use the "For iPhone/IPad" link to a short SDR video of a black image. Let the video menus and the home bar disappear and you'll see that the display will still emit a certain light. You can test this with different brightness levels of the display.
A more interesting test is this one:
Make sure to open it in the YouTube App so that it uses the HDR option. With HDR on and brightness to 100% black remains black and only the little white dot and the channel banner in the right corner is lit up. With brightness at 50% you can start to see flickering/a grayish background on the right and left side of the display, outside the 16:9 ratio of the video (see the first picture, I had to crank up the brightness all the way up to make it visible).
As you can see, the middle area of the display is perfectly black (as it should be for OLED), but the sides struggle to match this blackness and flicker between a light emitting state and a non-light emitting state. This makes me believe that it is more of a software issue, rather than a hardware issue, since the displays are clearly capable of displaying true black.
You can test this with different sets of brightness levels and will see that all, except for 100% brightness, show some kind of this behavior.
Now what's interesting is, that when you have the video paused and look for the issue, the display correctly converts the blacks to true blacks, but when the video is running, the elevated blacks are there again.
The final test you can make is to now put your phone into battery saving mode (this disables HDR video on the iPhone) and watch the same video again. In this mode the whole display now emits a glow or flickers depending on your brightness level.
(See the second picture, again, I had to crank the brightness all the way up to make it visible in the picture and I used night-mode camera of the iPhone, so its not
that crazy looking in real life, like in the picture.)
Lastly, I recorded a little clip of this video (displayed in SDR mode) with the 12 Pro camera and cranked up luminance, brightness and lighting in post-prod to make it
somehow visible in video form.
The video is paused and at first you can see the whole screen glow like in the second picture, but after a couple of seconds the screen glow disappears and the phone displays a true black background (as OLED should).
Watch when it changes from 0:13 to 0:14 seconds right at the end, afterwards the camera tries to refocus again. You can still see the white dot and the red logo, but the black background changed from the dark glow to a complete OLED true black. Unfortunately, this behavior does not translate when the video is playing, so we are left with a glowing "black" instead of the true blacks of OLED displays.
The test with the HDR video leads me to believe that something on the software side is bugged and iOS has issues with addressing the correct HDR/SDR conversion of content on the display. The displays are clearly capable of displaying a true black image when certain circumstances are given.
Also the fact that this issue happens on my 12 Pro and my 12 Pro Max (which, based on the serial number, were manufactured at different factories), leads me to believe that either, I got incredibly unlucky and got two hardware failures in a row from two different manufacturing batches and across two different models, or it is indeed a software issue.
(Or, I guess, the third possibility is that all the displays are completely ****ed and every iPhone sold from launch till now has these defective screens, which would mean that Apple just shipped millions of hardware defect displays on their new phones. But I think that is indeed the less likely possibility.)
