In essence, most notably on Forest Colony, when you are being hit, your entire screen fades to black so that all you see is your HUD elements. This makes tactical awareness nonexistent. I don't know if it happens everywhere, but I notice it most prominently near (but outside) the cave.
The image below is a good example of how things look. And actually, if anything, it may be even darker than that. I get it in both the snow and standard versions.
