Fallout 4 has just been released and I’ve been stuck fighting a lighting issue rather than raiders due to stretching the game to widescreen, a massive 3440×1440 due to having an LG ultra-wide monitor, the 34UM95. I’m not sure if this happens with smaller 21:9 widescreens notably 2560×1080, but the lighting has been confirmed to break with a resolution of 5760×1080.
This error typically only happens indoors where there’s a lot of shadows and lights within a small area, but it’s incredibly annoying as it takes up a good third of the screen.
I’m not even sure why Bethesda didn’t support ultra-wide monitors in the resolution selection but there are quite a few of us out there with larger unconventional monitors. To even get the game to run in fullscreen on my monitor I went into ‘Documents’ > ‘My Games’ > ‘Fallout 4’ and then edited the Fallout4Prefs.ini fields to this:
iSize H=1440
iSize W=3440
The above directory is on windows 7 and may differ if you have an alternate operating system.
Now to fix the lighting. If you’re using an ultra-widescreen monitor with Fallout 4 you’ll have go into the ‘Prefs’ file like above and set:
bComputeShaderDeferredTiledLighting=0
Here’s some screenshots of the lighting surface that appears amidst some lights:



There will still be a couple of bugs in the game such as the sniper scope image below, but the lighting one is the most noticeable.

This also occurs when running at 5760×1080…
I’ve got 3 screens in portrait orientation instead of landscape (ultrawide) at a resolution of 3240×1920, and also have this problem. The aspect ratio is very near a 16:9 aspect ratio. I have a feeling the problem happens at any resolution above 1080.
Thank you…. you saved my life
This is terrible, it makes the game look worse when you change the pref thing from 1 to 0.
Guys, it’s better to download and install Better High-Tech Lights – on-off switch bugfix and more
In fact,t here’s 2 mods like this on the nexus. That will fix everything.
This fix was long before any mods were out, to temporarily fix the lighting until Bethesda patched it or a mod was released. It’s probably outdated now or patched.