Theater Stage Lighting Upgrade Case

The problem as it presented itself

The brief was a specification, not a failure: the customer needed an illuminance figure guaranteed at the task plane, and the existing installation delivered a compliant average with unusable uniformity. The average number had been measured from a single point at the centre of the room, which is the first thing to check in any lighting complaint.

The diagnosis came from a measurement grid rather than a specification sheet. Taking readings on a grid across the working area showed the problem was geometric, not photometric: the fixture spacing was too wide for the mounting height, so the centre of the room was over-lit while the areas where work actually happened fell below target.

• Measure on a grid, not at a point. A single centre reading hides exactly the problem that matters.
• Check spacing-to-mounting-height before changing fixtures. Most uniformity complaints are layout problems.
• Separate the average from the task plane. Illuminance at floor level says little about illuminance at the work surface.

The fix was a layout change rather than a product change: closer spacing and a different mounting height brought the whole working plane into range. No luminaire was replaced. This is why the geometric check comes before the product check.