Scope and starting point
A beam-angle label usually describes a level within a distribution, often half of peak intensity. It does not describe a hard edge. Source size and lens alignment alter the beam. Use the actual IES/LDT or ray file and installation geometry, then verify illuminance at the required plane.
Selection notes
Use the exact order code and regional configuration. Compare delivered lumens, input power, distribution, CCT, color quality, dimming and installation constraints. Emitter efficacy cannot be substituted for complete-luminaire efficacy. Verify the official photometric file and mounting instructions.
Keep a reproducible record
Save the complete part number, source revision, operating point and the reason for each decision. Keep calculated examples separate from observed results. A measurement report needs its sample identifier, instrument and calibration details, stabilization, ambient conditions, raw record and uncertainty statement. Do not replace a missing value with zero or a typical value with a guaranteed limit.