What’s in a beam?

Singapore, 17th February 2011

I may as well follow up on yesterday’s blog in regards to lighting standards. One of the other big misconceptions is when guides specify a certain beam spread. It’s not that simple. Specifying a, say 24 degree beam does not really tell you how the full light distribution looks like. Many uninitiated assume that a 24 degrees means that the actual light beam happens within a 24 degree cone. Unfortunately in architectural lighting that is not the case. Theatrical spots do have that distinction where you can actually focus the light to a cut off at 24 degrees but in traditional architectural lighting that is not how it works.

So first we need to understand what 24 degrees means! In most of the cases it means that at 12 degrees either way from the peak intensity you will find half the peak intensity. This is done so you know what the related cone diameter is at half peak intensity at various distances away. If you wish to create an even light distribution with ceiling down lights for instance, you just need to space the lights at the length of the (50% intensity) beam diameter. A simple but effective way to space out your lights without complex calculations for multiple light applications.

What it does not say however is the lighting effect of the single beam, in other words what you see! The zonal light distribution will show you in some cases that lamp may have a 24 degree beam but that the furthest light away from the peak intensity may actually happen at 60 degrees, in other words the light projection that we see will have a clear peak brightness in the centre, but gradually fade of well beyond the projected 24 degree. A 24 degree beam is a technical description, but not representative of the visual beam effect! Without understanding the zonal light distribution, a technical beam degree does not mean much.

My pick for Light Watch today is a place where light distributions are crucial! I read today that Singapore opened its doors to its newest cultural hub over the weekend, the Art Science Museum located at the new Marina Bay Sands. I have yet to visit the place but surely lighting will be elementary, Watson!



Light Watch 34:   Art Science Museum at Marina Bay Sands, Singapore

17. February 2011 by Martin Klaasen
Categories: light watch, lighting and culture, lighting standards | Leave a comment

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