My room has white foam over the window with black out curtains cut out to the size of the frame stapled directly to the wall, with heavy duty tape on the edges to prevent any light bleed. All the electronics in my room get unplugged when not in use, and my door has a gap sealer on the bottom to prevent light from the hall getting in. It is as dark as is reasonably possible. However, I do turn on light directly near me when I am using bright monitors, just to keep the dynamic range of my environment a bit smaller.