Subject: IESNA versus CIE photometry

From: [email-masked] (Ian Ashdown)
Date: 29 Aug 1995 12:41:26 -0400

CIE Publication 102-1993, "Recommended File Format for Electronic Transfer
of Luminaire Photometric Data," clearly and unambiguously defines three types
of photometry: A (alpha), B (beta), and C (gamma). The accompanying diagrams
leave no doubt as to how their photometric webs are oriented with respect to
the luminaire.

IES LM-63-1991, "IES Standard File Format for Electronic Transfer of
Photometric Data and Related Information," on the other hand, is less
helpful. It refers the reader to the IES Lighting Handbook for a description
of Types A and B goniophotometers, and to CIE 27-1973 ("Photometry of
Luminaires for Street Lighting") and CIE 43-1979 ("Photometry of Floodlights")
for a description of type C. It then says that "Type C is the form in common
use in the United States (although it was formerly referred to as Type A)."

As best as I can tell from the descriptions in LM-63-1991 (and comparing them
to CIE 102-1993), it appears that the IES Type C is equivalent to the CIE Type
A, and that the IES Type A is equivalent to the CIE Type C. Is this correct?

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