Bought these for east facing window. Yes, they definitely block the light. My complaint is they don't hang well. The fabric is soft but poufy and while they pleat ok at the top, about halfway down they just billow out. Tried holding them together at the bottom with the tieback for a few days, but that didn't help. I just prefer a more tailored look, I guess. The photo shows them hanging nice and straight but mine didn't and still don't after 3 weeks.