[this could be in a Lighting Components sub-forum]
I use up-lighters a lot in the events we produce, and needed a spotlight guide to judge light intensity.
I have begun testing a basic floor can, used to colour wash walls. I have positioned the cans at a different distance from the wall (50 cm increments), and at 3 different angles (up, 5 deg. towards wall, 10 deg. towards wall).
I wanted to see the effects both on the wall and the ceiling, and have a useful tool to choose which light to use, depending on what is needed.
Attached is the resulting render, and .skp file (settings are in there). As I said, its mainly for my needs, but I thought it could be useful for those who use down-lighters (just invert the scene, insert your own light, and play with spotlight size / intensity), or for any other reason.