How to Validate Photometric Files Before Uploading to Your PIM

Why photometric validation matters

A bad photometric file does not cause an obvious error. It silently produces wrong lighting calculations. A lighting designer uses your file to calculate illuminance levels for a warehouse. If the file has a truncated candela table or a wrong lumen value, the calculation shows adequate light levels where the real installation will be too dim. The customer blames the fixture. The designer blames the data. The distributor handles the return.

Photometric data is also one of the most common missing assets in lighting product catalogs. When files are present, they are often outdated (from a previous LED generation), mismatched (attached to the wrong product), or structurally broken (from a bad export or conversion).

Validate every photometric file before it enters your PIM. Start by running the file through the photometric file validator to catch structural issues automatically.

Step 1: Collect files from manufacturer or lab

Photometric files originate from two sources:

Goniophotometer measurements: A photometric lab measures the luminaire on a goniophotometer and produces the raw data file. This is the most reliable source. Request the file directly from the lab or from the manufacturer's engineering team.

Manufacturer product data packages: Many manufacturers distribute photometric files alongside their catalog data, either as individual file downloads, in ZIP archives per product family, or via data exchange platforms like DIAL LUMIDAT or RELUX.

Confirm the file matches the product. A common error is receiving a photometric file from a previous product version (different LED module, different optic, different lumen output) attached to a current product listing.

Step 2: Run structural validation

Structural validation checks whether the file conforms to its format specification.

For IES files:

• The file starts with IESNA:LM-63 (or IESNA91, IESNA:LM-63-1995, IESNA:LM-63-2002)
• The TILT line is present and valid
• The data line declares the correct number of vertical angles (Nv) and horizontal angles (Nh)
• Exactly Nv vertical angle values follow
• Exactly Nh horizontal angle values follow
• Exactly Nv x Nh candela values follow

For EULUMDAT files:

• Line 4 declares the number of C-planes (Mc)
• Line 6 declares the number of gamma angles (Ng)
• Exactly Mc C-plane angle values appear
• Exactly Ng gamma angle values appear
• Exactly Mc x Ng candela values follow the angles

The most common structural error is a mismatch between declared angle counts and actual data. Upload the file to the photometric file validator and check for angle count errors.

If the file was generated by converting between formats (IES to LDT or vice versa), conversion errors can truncate or duplicate candela rows. Always validate the converted file independently.

Step 3: Check metadata quality

Metadata determines whether the file can be matched to a product and whether lighting design software displays useful information.

Required metadata:

• Luminaire name (identifies the fixture in lighting calculations)
• Catalog number / article number (matches to your PIM product record)
• Manufacturer name

Important metadata:

• Lamp/LED module description (wattage, lumen output, color temperature)
• CRI (color rendering index)
• Input wattage (total system wattage including driver)

In IES files: Check the [MANUFAC], [LUMCAT], and [LUMINAIRE] keyword lines. Missing or generic values like "Test" or "Sample" indicate the file was not properly labeled after measurement.

In EULUMDAT files: Check lines 1 (company), 9 (luminaire name), and 10 (article number). Empty lines or placeholder text mean the metadata was not filled in.

Fix metadata issues by editing the text fields directly. IES keyword lines and EULUMDAT metadata lines are plain text. Update them to match your product records. Do not modify the numeric data.

Step 4: Verify luminous flux consistency

The declared luminous flux (in lumens) should match the flux calculated from the candela distribution. Lighting design software uses the declared lumen value to scale the intensity distribution. If the declared value is wrong, all calculations scale incorrectly.

How to check: The theoretical flux is calculated by integrating the candela distribution over all solid angles. Most photometric software (DIALux, Photometric Toolbox, EULUMDAT Editor) can compute this. Compare the computed flux with the declared flux.

A mismatch of more than 5% suggests a problem:

• The declared lumens are from a different LED module version
• The candela data has been scaled but the lumen value was not updated
• The measurement used a different lamp than the declared one

In IES files: The lumen value is in the data block (lumens per lamp x number of lamps). The candela multiplier is also applied.

In EULUMDAT files: The total flux is on line 16 (lumens per lamp set).

Step 5: Check for anomalous candela values

Scan the candela data for values that indicate measurement or export errors:

Negative values: Candela values must be zero or positive. A negative value is always an error (data corruption or export bug).

All-zero planes: A C-plane where every candela value is 0.0 usually indicates a measurement error or a file truncation. Unless the luminaire genuinely emits no light in that direction (unlikely for a full C-plane).

Sudden jumps: Adjacent angle values should change gradually. A value that jumps from 1500 to 15000 and back to 1500 suggests a decimal point error (one value is 10x too high).

Symmetry violations: If the file declares symmetry (e.g., C0-C180 symmetry), the candela values for symmetric angle pairs should match. If C0 at gamma 30 reads 1200 and C180 at gamma 30 reads 800, the symmetry declaration may be wrong, or the data may have been manually modified.

Step 6: Validate physical dimensions

Photometric files include luminaire dimensions used by lighting design software for area source calculations and 3D rendering.

In IES files: Width, length, and height are in the data block (fields 8, 9, 10 of the main data line). Values are in metres or feet depending on the units flag.

In EULUMDAT files: Lines 20-22 carry length, width, and height in millimetres.

Check that:

• Dimensions are non-zero (a zero dimension causes rendering issues)
• Dimensions are reasonable for the luminaire type (a recessed panel should not be 5 metres long)
• The units are correct (metres in IES, millimetres in EULUMDAT)

Step 7: Test in lighting design software

After automated validation, open the file in DIALux, RELUX, or your preferred lighting design tool. Check:

• The luminaire renders with the correct shape and size
• The light distribution pattern looks correct for the fixture type (a downlight should show a cone, a batwing distribution should show two lobes)
• The total flux displayed matches the declared value
• The LOR (light output ratio) is reasonable (typically 50-100% for LED luminaires)

If the distribution pattern looks wrong (light going upward from a recessed fixture, asymmetric pattern from a symmetric luminaire), the file may have incorrect angle assignments or the tilt specification may be wrong.

Step 8: Upload to PIM with product matching

When the file validates cleanly:

1. Name the file consistently: use the article number as the filename (e.g., RLP-600.ldt, RLP-600.ies)
2. Upload to the correct product record in your PIM
3. Record the photometric file version/date so future updates can be tracked
4. If you provide both IES and LDT formats, upload both and verify they produce the same results

Worked example: validating a batch of LED panel files

A luminaire manufacturer sends 150 LDT files for their LED panel range. Your team needs to upload them to the PIM.

Running all 150 through the photometric file validator:

• 142 files pass structural validation
• 5 files have angle count mismatches (truncated candela tables)
• 3 files have empty luminaire name fields (line 9)

The 5 truncated files were corrupted during ZIP compression. Request replacements from the manufacturer. The 3 files with empty names can be fixed by editing line 9 to match the product article number in the PIM.

After fixes, re-validate all 150 files. Then spot-check 10 in DIALux: open each file, verify the distribution pattern matches the fixture type, and check that the total flux is consistent with the datasheet.

Upload the validated files, linking each to its product record by article number.