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Q&A: IES File format

Question
IES File format

Synopsis
IES File format

Solution
“I have attached an example IES file to help me to respond to your question. Please make note of the fifth line in the file:

1 10.000000 1.0 19 1 1 1 0 0 0

These values in the IES file, from left to right, represent the following (items 3.4 through 3.13 in IESNA LM-63-95):

1 = number of lamps
10 = lumens per lamp
1.0 = multiplier
19 = # of vertical angles
1 = # of horizontal angles
1 = photometric type (1= = Type C)
1 = Units Type for luminous dimensions (1 = feet, 2 = meters)
0 = Width across the luminous opening
0 = Length across the luminous opening
0 = Height across the luminous opening

It is true that the TracePro-generated file has a “1” indicating that the units are in feet (rather than a “2” for meters). This selection of units applies to the Width, Length, and Height of the Luminous opening, which TracePro does not report (cannot be determined from the ray trace data).

The raw data generated from the TracePro ray trace in Lines 7, 8, 9, and 10 of the IES file are the angles in degrees and the intensity in candelas. Candelas are lumens/steradian, which only has an angular dependency, so linear units (feet vs meters) are not relevant for this data.

In conclusion, the IES file produced by TracePro provides Intensity data in a format that would be useful to you. If the width, length, and height of the luminous opening were needed in the IES file, the file could be opened in a Text Editor (e.g. – Word, WordPad, NotePad, etc), Line 5 could be edited with the Luminous opening dimensions, and the “1” for feet could be edited to a “2” for meters if the units of the luminous dimensions were given in meters.”

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