Gamma comes higher when starting Gmod

I have weird issue with Gmod. When i start Gmod my gamma or brightness becomes higher for some reason. My settings in options is default. I never changed brightness and even if i adjust it, it does not give me desired effect. Btw, setting option to “window mode” makes gamma correct, but i dont want to play in window. I tried other games in Steam and they work fine, gamma does not change.

Can someone help me with this shit? It makes me mad!

does anyone knows what is the problem?

are you sure you havent any effects on thats what happend to me btw post processing?

Well i dont have gamma issue in window mode! Or PP works only in fullscreen mode? Anyways i reinstalled gmod and gamma still fucks me! So where is that setting or config stored? And how can i check what is my PP option?

turn off the bloom option
maybe it will fix it

No it didnt help.