Definition
An IES file (IES LM-63 format) is the standard digital container for photometric data — it describes how a luminaire distributes light in three-dimensional space. Created by measuring the complete luminaire (not just the LED chip) on a goniophotometer, the IES file contains: luminous intensity (candela) at thousands of angular positions (typically 2.5° or 5° increments in vertical and horizontal planes), total luminous flux (lumens), luminaire dimensions, lamp/luminaire classification, and photometric test report metadata. Lighting design software (DIALux, AGi32, Relux, Calculux) imports IES files to perform accurate point-by-point illuminance calculations, producing lux grids, uniformity ratios, and glare ratings that determine whether a lighting design meets code requirements. For B2B procurement: an IES file is the difference between guesswork and engineering — without it, you cannot verify that the proposed luminaires will meet the specified illuminance requirements.
Key Data
| Parameter | Value / Explanation |
|---|---|
| Format | IES LM-63 (current: LM-63-19). ASCII text file, typically 50-500KB. |
| Contains | Candela values at angular grid points, total lumens, luminaire dimensions, test lab info, lamp specs |
| Measurement method | Goniophotometer — absolute photometry (complete luminaire) per IES LM-79 |
| Angular resolution | Typically 2.5° or 5° increments. Finer = more accurate but larger files. |
| Software that uses IES | DIALux (free, most popular), AGi32, Relux (free), Calculux, Visual, Radiance |
| Why B2B needs it | Required for lighting design compliance verification — building permit submissions often require photometric calculations |
Application Guide
Office lighting design
Request IES files for all proposed luminaire types, run DIALux simulation
Verify 500 lux maintained at 0.8m working plane with UGR ≤19 per EN 12464-1
Warehouse layout
IES files for high bay types, simulate at actual mounting height and spacing
Verify 150-200 lux at floor level with uniformity ≥0.4 per IES RP-7
Outdoor/parking lot
IES with Type III/IV/V distribution, simulate at actual pole height and spacing
Verify maintained illuminance and uniformity per IES RP-8 or local municipal code
Conclusion & Procurement Recommendation
For B2B procurement: IES files are non-negotiable for any project requiring lighting design verification. Key specifications: (1) Request IES files from absolute photometry (complete luminaire tested per LM-79), not relative photometry (calculated from component data), (2) Verify the IES file matches the exact luminaire configuration being procured (same LED, driver, optics, and CCT — different CCTs have different lumen outputs and require separate IES files), (3) For tunable-white luminaires: request IES files at minimum, mid, and maximum CCT settings, (4) Require photometric calculations as a contract deliverable — the lighting designer or manufacturer must provide DIALux/AGi32 reports showing compliance with the specified illuminance criteria.