Lighting in GMod and Half-Life 2

Is there a reason why the lighting in my games looks like this?

For some reason, areas look like they have pools of shadows in areas and also have a strange discoloration. Also strange is that in areas where it is lit, objects are completely dark. Is there an explanation for this and is there a way to fix it?

thats a result of the new 2009 source engine update to hl2 that messes up with the engines way of handling lighting
everyone has this problem whether they realize this or not - often passing it off as “nope i dont have this” out of some feeling of self righteousness

I’ve actually never even noticed this. What map is that on?

This is actually a Left 4 Dead map ported over to Garry’s Mod. Found here:

This isn’t limited to this map though, but almost every map.

i would probably fuck with the lightmaps or something

the maps need to be compiled to have hdr for that problem to be fixed
since 70% of hl2 maps have no hdr, and most l4d ports have none of it, the problem will remain

only the mapper can fix this