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
Match the emitter package, light-emitting surface and mechanical reference points to the optical part. Review intensity distribution files rather than only the named beam angle. A lens family can contain many distributions; the result changes with source geometry, spacing and cover materials.
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.