I am very to the unreal engine but I have been messing around a lot in UE5 when I discovered some annoying bug with emissive lighting.
So basically, I was messing around with emissive lighting in UE5, when I noticed that emissive lighting leaves weird lighting artifacts for a very short period of time, I cannot remember seeing such artifacts in when I tried UE4 so I decided to make a quick test level, it turns out I was right, the artifacts dose not appear in UE4 the same way as it does in UE5, I also converted the project to UE5 and the artifacts were back. after a lot of tinkering with different settings, I noticed that the artifacts disrepair when I reduced the anti-aliasing quality to normal, so naturally I tried FXAA and Nvidia DLSS, and they both work completely fine.
TLDR: TemporalAA does not interact properly with Emissive lighting in UE5.
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just to show what the bug looks like from both UE4 and UE5’s POV
if anyone knows how to fix this without switching to UE4 / using FXAA/DLSS
then I would appreciate it if you can tell me a solution, and thanks for reading 
