This question has been answered by Alan Tulla, Lux Review technical editor.
Backlit panels deliver improved efficacy – plus you can do more with an LED array covering a 600 x 600 square than you can with 2400 of LED tape.
Table 2 of the ILP’s guidance notes for the reduction of obtrusive light calls for a 0 lx restriction for zones E0 and E1 (dark and intrinsically dark environments). But how is 0 lx achieved, and can 0.5 lx be rounded down and considered to be 0 lx?
I have always understood that 0 lux means no artificial light. In other words, after curfew, the lighting is switched off. This is a common situation and easy to achieve. In practice, you will find that trying to reliably measure values which achieve a mean value < 0.5 lx is almost impossible. Don’t do it; just switch the lights off. That way, you are certain to conform to the ILP guidance.
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