Question

We have an HID light fixture that has a luminous diameter of 18 inches. What is the number of footcandles found at a point that is 4.5 feet over from the center of the fixture and 12 feet down? The candlepower distribution curve for this fixture is as below in Table 1:

? - I

0 - 8564

5 - 8817

15 - 10964

25 - 12534

35 - 11845

45 - 9025

Table 1

Answer 1

Information about a fixture's light distribution is also generally available in a file format that can be loaded into an analysis or rendering program and used to help better understand the lighting within a space. There are a number of different file types, the most popular of which are listed below.

IES is the international standard file type for providing luminaire light distribution information. The standard was developed by the Illuminating Engineering Society of North America (IESNA), which has simply become the Illuminating Engineering Society. IES files have a .ies file extension.

EULUMDAT is the main format used in Europe. The standard was originally developed in Germany, but there is currently no official documentation on the format. EULUMDAT files have an .ldt file extension.

CIBSE is a format used primarily in Great Britain and is published by the Chartered Institute of Building Service Engineers. CIBSE files have a .cibse file extension.

LTLI is a format occasionally used with Autodesk products such as 3ds Max. LTLI was developed by the Danish Illuminating Laboratory and is the standard used in Scandinavian countries. LTLI files have an .ltli file extension.