S21 Ultra Dimming Issue in Strong Light

[pioneersti]

I'm hoping someone here can tell me whether this issue is caused by hardware (screen/motherboard ) or by software, and if it is a software issue how to solve it. For reference the screen works perfect, and the adaptive brightness function works good indoors going from darker rooms to brighter rooms.

The video linked below shows the Galaxy S21 Ultra (right) side by side with a Galaxy S20 (left) to highlight an issue with the adaptive brightness. When light is applied the S21 Ultra starts to get bright, then dims right down and slowly increases in brightness again, but never gets as bright as it was just before the strange dimming. You can see the S20 is brighter than the S21 Ultra, which shouldn't happen. This can again be seen when the light is removed. If you take both phones outside in direct sunlight, the S20 is brighter than the S21 Ultra. If adaptive brightness is turned off on the S21 Ultra, and the brightness manually set to all, it is a bit better in direct sunlight, but still not quite as bright as the S20.

https://youtu.be/cEt6VcF-hiM 

[Joeeye]

From what I see, the light is firmly above the S21 Ultra directly. You can tell by the reflection of light at the top of the S21 with little to no reflection over the s20. This test doesn't convince me of anything different in the handsets behaviours.

[pioneersti]

The light is directly above both phones. My wife is to the right and obviously the angle of her phone recording will change where the reflection displays. The phones behave the exact same way in direct sunlight next to each other, so unless I can somehow move the sun, the 'test' you see here represents what happens in the real world situation. I didn't do the test because for no reason I suddenly decided to hold a bright light 12 inches above my phones and discovered this problem. I did because I could always see my S20 outside in bright sunlight but can't easily see the S21 Ultra. Recording the test indoors allowed me to show the screens go from dim to bright to dim, and clearly show the issue. I did it because when I go out into sunlight the S21 Ultra gets bright, then dims down and then comes back up bright, but not as bright as just before it dimmed. This is a real problem and with respect, I need suggestions and/or solutions.

[Joeeye]

The simple answer, heat and power. Smaller phone, smaller screen, slightly lower maximum brightness, means less power used and heat generated. Typically most large phones do not maintain their peak brightness and the S21 Ultra is no exception. The fact it can and does reach a higher peak means that there will always be a wider variance from it's highest setting. Having said that, I've also tried to recreate your experiment but found my S21 Ultra did not exhibit this brightness shift. My guess then is at the time of your test, your device must have been operating at a much higher temperature than my own unit.

[pioneersti]

Thanks for the reply.

Believe me I have checked everything to make sure nothing unusual could be causing the issue. I basically took the phone from idle doing nothing, and with Devcheck open showing the battery temp was low and CPU temp was low (both below 40ºC), walked outside and the issue still occurs. Screen was still cold to the touch from being off for a while in an air conditioned room. When the test was done indoors with the light everything was cold. I even checked the light sensor to make sure the lux reading was increasing with more light. I did a factory reset and still same thing, so I'm thinking it's hardware related. I guess the only options now are either to just live with it and place the phone on manual full brightness whenever I need to use the phone outdoors on a sunny day, or send it to Samsung for repair.

[Joeeye]

Is it running One UI 6?

[pioneersti]

Sorry for late reply.

No, it's running One UI 5.1.

So far I tried clearing the cache, then tried a factory reset, but that didn't work. Even though I was 99.9% sure it wouldn't be the cause, I also reloaded the stock firmware. Same issue.

I'm taking it to an authorized Samsung dealer tomorrow, and let them diagnose it.

At this point I believe it's either the display itself, or (hopefully not) the motherboard. I had an S9 in the past with a strange display problem that turned out to be the motherboard.

I will update the thread with the results of their diagnosis.