Abstract
The distributive principle is inapplicable to loci of scalar utilance and cylindrical utilance. The British Zonal classification system therefore cannot be used for predicting these quantities; despite this limitation it is concluded that a more widely applicable system of luminaire classification would be unacceptably complicated. Nomogram grids are presented which enable lines of limiting vector/ scalar ratio to be drawn on luminaire domain charts. Every locus of constant vector/scalar ratio in the luminaire domain is also a line of constant wall/task illuminance ratio and a line of constant horizontal/cylindrical illuminance ratio. In a given interior these ratios cannot be independent criteria; each can be expressed in terms of either of the others.
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