Yes I have read the above article and was trying to calculate what I would need from the 4 x 4m that was used as an example. I forgot to mention the room was measured in ft. I looked it up and from what I read is that 1 meter = 3.28084 Feet. I am guessing around 1800 lumens. Also I don't know if this makes a difference or not but that room has blue walls. The ceiling is white though.