Lighting Lux & Coverage.

Lumens measure the total light a fixture puts out, while lux measures how much of that light actually lands on a surface (one lux is one lumen spread over one square metre). A bright fixture with a wide beam or a long throw can still give you low lux on the stage, which is why this calculator works out lux at the throw distance rather than just quoting the fixture's lumen rating.

As a rough guide, allow about 300 lux for general ambient or audience fill, 500 to 800 lux for presenters and speakers so faces read clearly, and 1000 lux or more for broadcast and camera key light. Drama and theatre often sit lower for mood, while a brightly lit conference or trade stand needs the upper end. Always treat these as starting targets and adjust for colour, camera and the look you want.

Beam angle is the spread of the cone of light a fixture throws, measured in degrees. A narrow beam (say 10 to 15 degrees) concentrates light into a small, intense pool, while a wide beam (40 degrees or more) spreads it over a larger area but at lower lux. Widening the beam or pushing the fixture further back covers more stage but trades away brightness, so it is always a balance between coverage and punch.

Light follows the inverse-square law: when you double the throw distance, the same beam covers four times the area, so the lux on the surface drops to a quarter. That is why a fixture flown high over a large stage delivers far less light than the same unit a few metres away. This tool applies that relationship so the lux figure reflects your actual throw distance, not the lab rating.

Work out the beam diameter at your throw distance, then divide the area you want lit by the footprint of one beam to get a starting count. In practice you should add roughly 30 to 50 percent more fixtures so the pools overlap, because butting beams edge to edge leaves dark gaps and uneven hotspots. Use the calculator's 'blanket area' figure as a minimum and plan for overlap on top of it.