Describe the bug
This mod lags on fancy preset, but te FPS are high.

To Reproduce
Steps to reproduce the behavior:

1. Load Minecraft with this mod
2. Set Dynamic Lights: Fancy
3. Play Minecraft with a torch in the hand
4. Lag, but the FPS are still high

Expected behavior
I expected not to lag.

Screenshots
I cannot make a screenshot, because the FPS are normal, but the game lags.

Desktop (please complete the following information):

• OS: Windows 10 Home

• Minecraft 1.16.5

• Fabric Loader version 0.11.2

• Mods
  

• Version 1.3.4

• Branch mc1.16

link to video comparison?

Ok, thanks for the info

Without using other mods (in the videos the "lag" is seen less ...):
LambDynamicLights https://mega.nz/file/rZwkyAaT#4dhV47kkT95us0n1FnNWKfJkGodroMxqO8kNQQ0eEBg

OptiFine https://mega.nz/file/WUhmHSJC#a-hyIkSmyAesD0NDPSacH4GYBLs_1tSLVPJpbFgwGuo

Sorry, but the files are too big for GitHub...

Comparing a mod with the feature alone, and a mod with a bundle of features isn't fair.

The only reason it doesn't lag is OptiFine somehow makes chunk rebuild a bit faster.
You might want to try Sodium with Indium (note: it requires a fork of Sodium) so you can still use LambdaBetterGrass.