Arma3 Issue

[Roddy189]

Hey guys, 

 

for some reason whilst playing Arma3: Wasteland I keep getting a dark patch on screen that is in line with the top left to the bottom right corner of the screen, like a right angle triangle. top right half seems ok, but bottom left seems dark and makes it impossible to play whilst it's night. any ideas guys? slightly difficult to see with this pic but you can get the idea...

cheers. 

[Pugs501]