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IES

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IESNA LM-63 Photometric Data.

At a glance
Original creator Illuminating Engineering Society of North America (IESNA)
Purpose A luminaire's measured light distribution in the IESNA LM-63 text format: the candela values over a grid of angles, with keywords describing the test and the luminaire.
Extensions .ies
Poka parser poka-ies
Viewer poka-metadata-card-viewer
Depth tier Metadata card (see Depth tiers)
Breadth tier B3 Core (see Breadth tiers)

How much Poka reads

B3 Core. Only the main content type or types are decoded (for example geometry but not materials, layers or annotations, or only one version family). The list of gaps is substantial.

Confidence: medium (the reviewer read the code). Basis: Reviewed 2026-10-16: poka-ies lib.rs (parse_ies, build_ast, unit tests, tests/tilt.rs) and tests/samples.rs over 5 corpus files (3 x LM-63-1995, 2 x unversioned 1986-style ERCO). The numeric block is fully parsed and validated, but the card shows only counts, peak and derived totals. B4 would also be defensible, since the distribution itself is not displayed.

What Poka does not read

  • Candela distribution is not shown: no polar curve, no per-angle values, no angle lists (only grid size, peak intensity, rated lumens and efficacy)
  • Only about 7 keywords are shown (MANUFAC, LUMCAT, LAMPCAT, TEST, TESTLAB, ISSUEDATE, LUMINAIRE); all other keywords (MORE, OTHER, BALLAST, MAINTCAT and LM-63-2002 or later extensions) are only counted
  • TILT=INCLUDE tilt data is read and counted on the card, but no corpus file uses it (all five state TILT=NONE); the block is covered by synthetic tests
  • TILT=filename (external tilt file) is not followed
  • No derived photometric values such as beam angle or zonal lumens
  • LM-63-2002 and LM-63-2019 editions are untested (no corpus sample)

Background

Most lighting manufacturers publish their photometry in this IESNA format, which lighting design software loads to compute illuminance. Several editions exist and older ones are still common. The keyword header ends at the line that begins TILT=, not at a blank line — a keyword's value can mention a tilt file without ending the header — and after it come the counts, the angles and the candela values. TILT=INCLUDE puts a geometry value, a pair count and an angle and factor per pair in between; those are read as numbers, so a writer that wraps them differently is still read. Poka shows about seven named keywords (the rest are counted), the lamp and luminaire data, the size of the angle grid and the peak intensity on a metadata card; the candela values themselves are not shown.

Versions

Version Identifier Poka Note
LM-63-1986 Read No version line and no keywords; the description is taken from the header lines.
Later editions (LM-63-1995 and on) IESNA:LM-63-<year> Read

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

  • lidrs (candidate; MIT; Rust; https://github.com/sammorrell/lidrs) — Reads and writes LM-63 1986/IESNA91/1995/2002 and EULUMDAT; conversion to its PhotometricWeb struct implemented for type C photometry only; v0.2.3 (Jan 2026); no LM-63-2019 mention found
  • eulumdat-rs (eulumdat crate) (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Described as an LDT and IES parser/writer/validator; I could not confirm from its docs page how fully IES reading is implemented (feature list stresses LDT parsing and IES export); strong copyleft licence
  • eulumdat (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Eulumdat (LDT) and IES photometric file parser, writer, and validator for Rust; v0.7.1, updated 2026-09-18; matched on lib.rs, not tested
  • eulumdat-egui (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Cross-platform GUI application for viewing EULUMDAT/LDT and IES photometric files; v0.7.0, updated 2026-05-18; matched on lib.rs, not tested

Sources