This living room window faced due south and was dark and miserable and this was not helped by the large trees on that side which had no inherent reflectivity.
The room is now much more livable. Happy client.
In retrospect I would now advise a small amount of convexity be induced to give more penetration into the room and perhaps cut down the bushes against the window which by now (2015) will probably be shading the floor to a much greater extent.