Problems with Glare in the standard EN 12464-1:2011

Problem 1. Not a regular array

The standard says that the table method should be used for determining glare where there is a regular array, but offers little help on how to proceed if there is not a regular array and the table method is therefore inapplicable.
"If the tabular method is not applicable and the observer position and the viewing directions are known, the UGR value can be determined by using the formula. However limited research has been done to determine the applicability of existing limiting values. Limits for this condition are under consideration."
This means that the UGR limits stated in EN 12464 can only be applied to a regular grid of luminaires.
EN 12464 does not give any UGR limits for installations that do not have regular grids.

Problem 2. Calculation methodology for the tabular method

The limiting glare values specified in the standard are taken from another document where calculations are based on spacings that are different to those required by the standard.
EN 12464-1:2011
"The variations of UGR within the room can be determined using the comprehensive tables for different observer positions, as detailed in CIE 117-1995" (based on 0.25 spacing).
BUT the limiting values given in the standard are taken from ISO 8995:2002 clause 5 which is based on 1:1 spacing.
This means that the EN 12464 glare limit calculations are misleading..
Question: how many Glare Apples am I allowed?
Answer: 3 Glare Bananas!

References
CIE 117-1995 Discomfort Glare in Interior Lighting
"... uncorrected UGR values may be calculated for a reference spacing. This has been set at 0,25 x H ..."

ISO 8995:2002
"UGR values in clause 5 are based on the standard observer positions which have been validated by the UGR tabular method at a 1:1 spacing to height ratio...
...Clause 5 lists limiting values based on a 1:1 spacing ratio..."

CIE 190:2010 Calculation and Presentation of Unified Glare Rating Tables for Indoor Lighting Luminaires
"Calculation & presentation of UGR tables...
...The spacing to height ratio (SHR) is 1:1..."
References
CIE 117-1995
ISO 8995:2002

Not surprisingly, most people just don't understand UGR and rely on what is reported by Relux.
A Glare seminar is being arranged at the The Lighting Industry Association.
Glare Seminar details and booking information (opens in a new window)