by ccolley12 » Mon Oct 16, 2017 8:57 am
You need more information than what you have listed. These questions are typically referencing a specific light fixtures photometric chart. These show how much light is emitted. You then have to know at what height off the ground the fixture is mounted and then you can calculate the light levels at different surfaces.
Example.. Let's say you have a typical recessed light fixture in an acoustical grid ceiling (like the vignette) and the ceiling is 9' AFF. The table in your example would then be 6' from the light fixture. So you would look at the photometric chart for that fixture (and lamp being used) and see what the light levels are 6' from the fixture.