EULUMDAT

EULUMDAT is a widely used European photometric data format that describes the luminous intensity distribution of luminaires. The data are used to model how light leaves a fixture in three-dimensional space and are employed in lighting design software, CAD, and rendering engines.

The format is text-based and organized with metadata such as manufacturer, luminaire designation, lamp type, luminous flux, and color temperature, followed by sets of photometric data that describe the intensity pattern at specified angular samples around the luminaire. Data are typically tabulated in candela values for vertical planes and, optionally, horizontal planes, with angular steps depending on the file version. The common file extension is .ldt, and many manufacturers publish EULUMDAT files for their products.

Relation to other formats: EULUMDAT is one of several photometric data formats used in lighting design. IES photometric files (.ies) are more common in North America, while EULUMDAT has historically been favored in Europe. Both formats are supported by a wide range of software tools and enable similar types of lighting calculations, such as illuminance distribution, glare assessment, and rendering.

Uses and applications: The data enable accurate rendering and lighting simulations in design workflows, including calculating lighting levels on surfaces, evaluating light spill and glare, and integrating artificial lighting with daylight analysis. They are typically provided by manufacturers or lighting databases and can be imported into CAD and lighting calculation programs.

Standardization and availability: EULUMDAT originated in Europe as a practical data interchange format within the lighting industry. It remains a common alternative to IES files and is widely distributed by manufacturers and software vendors.