Well, my FP4 does get warm (not hot) often, at least more often than my previous Samsung, but it never complained about overheating (definitely not while using Google Maps!), and some of this warmth is most likely due to being in my (warm) pockets and having that metal chassis which readily conducts heat.
I’d vote “likely”.
If this is true, summer is coming and we should notice even more/stronger brightness fluctuations.
So really different things can make this happen, again even with a Custom ROM. not sure if it helps or make more complicated to figure it out. So everyone on FPOS could help by contacting support…
I’m experiencing this bug too. This rollout of Android 12 is horrible and the Fairphone team has also been horrible in handling it. The rollout was rushed, bug reports often get ignored and they don’t even seem to know how their own product works. I’m very, very displeased by this. I discover new bugs almost daily now, and I think it’s time to either install an alternate OS or refund the phone entirely.
Hi! Does anyone know the maximum nit level (brightness level) of the fairphone 4 I find it hard to see anything much on the screen in sunlight and it seems to be as bright as it can, kindest regards
JL
There seem to be some bug in sunlight that the brightness slider is at max however the screen dimms down so that you hardly see something. Please see above.
Exact same problem here on FP4 since last update
Really frustrating, the phone becomes unusable outside…
Hello, on my Fairphone 4, the display always darkens after a relatively short time. This happens especially when the Fairphone is used and heat develops through use. In my opinion, however, the time until darkened is very short. Especially when it’s very warm outside (I was on vacation recently and it was warm there. Sometimes the display went dark after just a few minutes.)
Is that normal? Can this be turned off or extended?
You mean the brightness slider stays at 100% while the displays dimms? Or can you do something to change brightness when this happens?
Yes. The Slider stays at 100% and the display dimms automatically . At that moment I cant do anything to increase the brightness. I could turn it down with the slider, but not up (because it is already at 100%). When it happens I can feel that the Phone is warm in the lower area. I close my phone then and after a few minutes when the Phone cooled down, the display turns the brightness automatically back again to normal.
It’s a very annoying bug that occurs since the android 12 update
Hello I have the same issue on my fp4 very annoying
On my FP4, problem seems solved with the latest update.
[edit] my bad, still here
The last few messages I got from support (from last Thursday and Friday) state that it’s still under investigation. So if it was fixed, it must have been something ported from AOSP along with Material You and probably wasn’t intentional. Like I wouldn’t mind, but I’d be very careful about claiming it’s fixed. 
I’ll definitely try replicating it again.
I’m pretty sure it hasn’t been fixed. Still exists for me.
Def not fixed 2 Minutes in the Sun and I dont see a lot
Funny enough I was able to make it happen just now, with a table lamp. Was holding my phone under a table lamp (75W equivalent) and after a couple seconds the screen went darker, slider still at full brightness.
Patch level FP4.SP28.B.065.20230420 (April 5th), phone wasn’t warm.
Tried to make it happen again, didn’t succeed, so there is a part of randomness in it (or some additional condition(s) besides illumination).
It has to be related to the brightness sensor at the top. Maybe it registers the infrared light that’s part of sunlight and then concludes the user has their face infront of the display?
I think you are confusing the ambient light sensor with the proximity sensor. And neither of them work like this. Some apps completely turn off the screen when the proximity sensor detects a near object. But that’s different than this dimming. This actually resembles the screen dimming on some OLED phones, where it’s a “feature” that helps prevent burn-in in hot conditions.
I see, that makes more sense. So it’s basically the display thermal-throttling itself?
Apparently it swings both ways! 
Yesterday evening I was using my phone in a dimly lit room (and the screen was consequently dim too), when all of a sudden, without apparent reason, the screen’s brightness went all the way to full!
Hiding the luminosity sensor with my hand didn’t change anything, the screen remained in full brightness till I switched the phone off and went to sleep. Phone wasn’t specially hot or cold either, it just happened, and it’s definitely the first time brightness goes randomly up for me.