The problem appeared after I upgraded the project from 5.4.3 to 5.4.4. I have no explanation why this is happening. The situation is identical when I open a new project, which leads me to the conclusion that the problem is in version 5.4.4. Any idea what could be causing the problem?
It looks like auto exposure. Try tweaking that in a post process volume. You can change the speed the camera takes to adjust, and how much it adjusts. Search for ‘exposure’ in the PP.
It’s not auto exposure. It looks to me like this is some kind of Lumen anomaly. There seems to be a huge delay in updating the lights on newly drawn elements, which appears as soon as I turn the camera. Problematic highlights appear randomly. I checked all available parameters for Lumen in PP volume, but nothing happened. I turned off virtual shadow maps just in case, but unfortunately none of those changes solved the problem. At this point, I’ve pretty much exhausted all the options I had in mind.
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Lumen does take time to update, unfortunately, but I’ve never seen it this pronounced.
How do you know it’s not auto-exposure? I say this, because it’s still the case that a PP placed in the level will not turn off AE. You have to actually set it on the player camera!
This has been going on since UE5… Also turning it off in the project settings does nothing 
To make sure that we’re on the same page, I’ll try to clarify this issue again. I didn’t turned off anything from the project settings and it’s not clear to me why you mentioned that. Regarding your suggestion, as far as I know, the last activated PP volume should override any other settings within the global PP volume or local PP volume settings on the camera. I believe that this is the basic purpose of the PP volume.
I have never had the need to adjust the AE on the player camera in the past, and that was not the case here either. I’ve been using Unreal Engine since version 4.12, and the settings I use for AE have been the same for years. So, I don’t see how AE could possibly be the reason for such a delay, especially if we take into account the fact that everything was working properly before the upgrade to 5.4.4. As for the specific settings within my project for AE, here’s how things are.
Basically, AE was not even in use here because Min and Max EV100 are set to 0, and the problem is present even after I disable AE on the camera as you suggested. So in my opinion this is not an AE problem, and it doesn’t look like it. It looks more like a Lumen problem. It seems to me that the settings for Final Gather Quality or perhaps some other parameter that regulates the work of Lumen are locked to the lowest values or something similar. The problem is also there while I’m working in the editor, not only when I start the gameplay.
In this example below, it can be clearly seen that the light calculation is performed very slowly and unevenly.
show the lumen debug views
Sorry, I’m not being clear
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There is an option to turn off AE in the project settings, it does nothing.
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Naturally, I’m familiar with the concept of PP volumes overriding each other. What I’m saying, is that the ONLY way you can successfully control AE, is with a PP on the player camera, set as you have it. ( Or that’s the only way I’ve been able to control it for several engine versions, in different projects ).
It might be worth just trying that on it’s own just to check it out.
The blotchiness is Lumen, for sure, I don’t know why you’re getting it so badly.
I just watched your most recent vid, much better example, you’re right that’s not AE 
But it might be worth being aware that controlling AE is a problem.
Summary
Whats happening with this window lighting up when you turn the camera?
Lumen scene looks fine, seems like parts of your scene are changing as you move the camera though which could be causing this.
Edit: Actually think I am wrong, this just looks like a viewport artifact from using spiral blur with against the scene texture in your glass material…
Really not sure what the issue could be. I would try disabling your post process volume and seeing if it improves, at least that will narrow it down to post process settings or not.
Also you didn’t change any of the cvars of the editor did you?
The lumen scene view looks correct and stable, weird for the final image to have those issues if lumen isn’t struggling behind the scenes. Seems like a migration bug to me, might just need to delete/undelete the post processing and/or lights or see if it’s happening in a new level.
That’s what I thought too, but here’s the funny thing. I reinstalled Unreal Engine and made a new project from scratch. The result was identical, even with the PP volume switched off.
At that point, I was thinking that it would be a good idea to try the same test with 5.5.0 preview, and I found that the problem was present there as well. This led me to conclude that the problem might not actually be the latest version of Unreal Engine as I originally thought, but maybe something else.
The graphics card I use is a Radeon RX7700 XT with the latest driver version 24.9.1.WHQL. After reinstalling the driver to version 24.8.1 the problem was solved.
I did not notice the problem because I installed the latest version of the driver almost immediately after I upgraded Unreal Engine to v.5.4.4. So far I’ve had 0 issues with the GPU driver and Unreal Engine, and this would be the first one. So I can confirm that there is a problem with the AMD 24.9.1 WHQL driver and Unreal Engine.
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