Found what is casuing lag/low framerate

Its the high dynamic range lighting option.
Disable and its fine but any other option causing lag/low framerate.
Seeing that this game can only run on 1 core when this happens core 1 usage skyrockets

any idea on how to fix
Game looks so much better with it on

my specs are fine
980X4.6
2 gtx 480

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.