Photometric Files and Data Sheets: What Buyers Can Actually Use

Lighting data arrives in several formats with different purposes, and buyers who cannot tell them apart end up specifying from a marketing sheet. The three that matter each answer a different question.

The three documents

A photometric test report measures what the product actually emits. A lumen maintenance projection estimates how output falls over time. An electronic photometric file describes the distribution of light in a format software can use.

A marketing data sheet is not a test report

Values on a product page are frequently derived, rounded or carried over from a previous version. When a specification matters, ask for the report and check the model number, the date and the laboratory on it, because a report for a different model is a common and expensive mix-up.

Distribution is the missing document

Output tells you how much light exists. Distribution tells you where it goes, and for task lighting the second is worth more than the first. A lamp with lower output and a well-designed asymmetric distribution will outperform a brighter symmetrical one at the same distance.

What to ask a supplier for, in order

Three requests, each of which a competent manufacturer can answer:

1. The photometric report for the exact model, including the colour data
2. The distribution description, or the data file if the specification is competitive
3. The lumen maintenance basis for the warranty period, with the test method named

Use it to compare, not to decorate

The value of photometric data is in comparing two products on the same basis. A report attached to a quotation and never used is a document; the same report used to disqualify an over-claimed alternative is a purchasing tool.