Every month I pick a product that’s been tested in our photometric lab in Cheltenham, run my eye over it and explain why it’s interesting, technically innovative and worth having in lighting schemes you might be planning. For over a year and a half, I’ve been writing exclusively about LED-based luminaires, to the extent that I think people have started to think of me as ‘that LED guy’.
Really I’m more of an optics and spectroscopy expert rather than an LED expert. The reason I cover so many LED-based luminaires is because that’s what people send me. This is partly because I’ve got a reputation as an LED expert, but it’s mostly a function of where the industry is going. We’ve all been to the trade shows and seen that almost every product on show is an LED luminaire of some sort. But we shouldn’t neglect the continued usefulness of other light sources (and if anyone out there has an induction luminaire that they’d like me to review, do get in touch).
To explain why I like the Noviled 600 x 600mm ceiling panel, I’m going to talk a little about discomfort glare, luminance limits and why this is important.
Are you sitting uncomfortably?
Discomfort glare is a metric that I’m sure most of us are aware of so I won’t take up too much space talking about it. It occurs when the luminance of a light is high enough compared with its surroundings for the lighting to cause visual discomfort for the people viewing it. This month I’m going to talk about luminance limits, which tend to apply to the specific case of office lighting. One of the problems that confronts lighting designers in office spaces is the reflection of high luminance objects in computer screens. Such reflections can be difficult because they mask the display or distract attention from it.
The guidance on this has been around for quite some time. I refer to the Society of Light and Lighting’s Code for Lighting and Lighting Guide 3 (LG3). The values I’m quoting here are also in the European standard EN 12464-1 on lighting for indoor workspaces. LG3 and the standard both say that the luminance should not be greater than 3,000cd/m2 at luminaire distribution angles above 65 degrees.
This value is a recommendation, not a hard and fast legal requirement. Unfortunately it is often taken as such, as the guidance document to the health and safety regulations states in its schedule of minimum requirements that people should treat LG3 as the point of reference for lighting. This creates a problem for luminaire designers, because it means that you have to create an office light source that stays below 3,000cd/m2 at all angles above 65degrees – and this isn’t something you can’t be sure of until you’vehad it photometrically tested.
We’ve all seen the consequences of this. Some designers try to get round it by making office lights with sharp cut-off angles, but this makes for highly directional schemes that make people feel like they’re working in a cave with a hole in the roof. I’ve tested ceiling luminaires where the manufacturer has been making frantic changes during testing (adding baffles, taking parts of the casing off) to try to bring down the luminance values. All of which is against the spirit of the original recommendations, which state that sharp changes in luminance distribution should be avoided.
So, it’s a pleasure to see someone create an LED-based 600 x 600mm ceiling luminaire that ticks the boxes of even luminance distribution and luminance limits while satisfying the usual metrics of high efficacy, good colour and high light output. As I’m sure we’ve all seen, this is a common approach where the manufacturer creates a thin, flat metal panel and mounts white LEDs in series around the edges. The panel is then covered with a white diffuser to spread the light out and the driver for the LEDs is mounted externally, so it can be hidden in the ceiling space when the fixture is installed. The NoviLED panel is an exceptional example of this technology.
The Noviled Alfa in numbers
The high lumen output and excellent efficacy compare with some of the best I’ve seen, and the high power factor adds to the excellent power efficiency. The colour is excellent, with the CCT of 3038K being perfectly acceptable for office environments. The low UGR of 20 means that this luminaire is well suited to all but the most demanding close-up work.
Excellent luminaire design has kept the luminance below 3,000cd/m2, well within the specified guidelines. The diffuser ensures that there are no sharp cut-offs of the light distribution, aswecan see in the polar plot.
Dr Gareth John is technical director of Photometric Testing, an independent lighting test laboratory that specialises in the photometric assessment of LEDs, luminaires, lamps and displays.
Check out review of 10 more great LED ceiling panels here
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