"Candelas Lumens and Lux" introduction to lighting  terms and calculations
"Candelas Lumens and Lux" introduction to lighting  terms and calculations
     
 

 

 

 

Eulumdat and Iesna: Length Width and Height specifications.

This article shows how length width and heigth of the luminaire and the luminous area are specified in LDT and IES photometric files. The clearest way of explaining this is by example using a long neon type light, in the LDT Eulumdat format

 

Eulumdaya size conventions

A fragment of the equivalent file is here:

LDT format Eulumdat

You can see that the length of the neon is along the C90 C270 axis.

The problem with IESNA files is that sometimes they have the length along C0 C180, sometimes along C90 C270. Sometimes it gets changed in Europe, because in Europe the convention is as the LDT file format, even though IES formats are used.

Officially:

IESNA Format (openings).

Exactly the opposite of LDT! An added complication (in the US format) is that linear sizes can be in feet or meters...

 

 
 
 
 

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