In the sun’s absence, darkness flourishes throughout the earth. Of course, we have lighting (illumination) to provide visibility throughout the night and indoors. Key to the effectiveness of lighting fixtures is a clear comprehension of its performance, as well as reliable communication of such photometric data. Specifying the data transfer, storage, and retrieval of this information is ANSI/IES LM-63-19: Approved Method: IES Standard File Format For The Electronic Transfer Of Photometric Data And Related Information.
What is Photometric Data?
Photometric data accurately displays the expected light distribution from a lighting fixture. Among other values, it includes two main units: total luminous flux and luminous intensity. Total luminous flux, or the amount of light emitted from a light source (and corrected for the human eye), is measured in lumens. Luminous intensity, as the lumens in a given direction, is measured in lumens per steradian (or candela).
Photometric Data File Format
Information regarding lighting fixture photometrics is conveyed in specific file formats. The files include information about light quantities, measurements, test reports, manufacturer, issue date, and luminous dimensions and shapes, as well as numerous luminaire performance values useful to 3D design. IES files are a commonly used photometric data file format, and they contain the .ies file extension.
IES, of course, is the Illuminating Engineering Society, an ANSI accredited standards developing organization. IES files derive from specifications found in ANSI/IES LM-63-19.
What is ANSI/IES LM-63-19?
The first line of any photometric file in the IES file format is IES:LM-63-2019, which distinguishes it from other file formats. It also marks the beginning of the file.
ANSI/IES LM-63-19, an American National Standard, describes the standard photometric data system and outlines how to build a file using this system. It outlines photometric data file formats specifically for data transfer, data storage, and retrieval.
Specifically, the standard document features a detailed description of data that can be used in the IES file format, along with programming and file conventions used in constructing and using IES standard photometric files. It also covers general rules for keywords, outlines and describes valid keywords, provides an example of an IES file, and describes luminous openings, lamp position, and the format for TILT=INCLUDE in its annexes.
Changes to ANSI/IES LM-63-19
Long proving to be a very useful and powerful standard for the photometric data file format, ANSI/IES LM-63-19 dates back to 1986. It is the fifth revision of the standard.
ANSI/IES LM-63-19 was revised with clarifications to make its use as simple as possible. It contains the following changes from the previous, 2002 edition:
- Definitions for photometric horizontal, photometric zero, absolute photometry, and relative photometry were clarified.
- The <future use> data field was changed to <file generation type> to describe how the file was generated.
- The TILT=<filename> option was removed.
- The [FILEGENINFO] keyword was added for additional information about the file generation type.
Future of ANSI/IES LM-63
As noted in the Introduction of ANSI/IES LM-63-19, this current edition is intended to be the final update to LM-63. The file format will be put into a long-term stability made, ultimately ensuring that it remains available as a reference. For the future of a standardized photometric data file format, ANSI/IES LM-63-19 states:
“This Standard will eventually be replaced by a new XML-based file format, ANSI/IES TM-33-18, Standard Format for the Electronic Transfer of Luminaire Optical Data […] However, both Standards are valid until this transition is complete and this Standard has been deprecated.”
ANSI/IES LM-63-19: Approved Method: IES Standard File Format For The Electronic Transfer Of Photometric Data And Related Information is available on the ANSI Webstore.
