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Light Distribution of Luminaires

There are a lot of important factors when choosing the right light fixture. We really care about the selections such as lumens per watt, color temperatures but how about light distribution?

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The importance of distribution of light is actually in the fixture itself. With the correct distribution of light, you can lower fixture counts and get a better sustainable project. Determining a luminaire’s light distribution can be also a key consideration. 
 
Light distribution is basically the projected pattern of light which is fixture can distribute onto a surface. Fixtures are available in wide variety of distribution patterns, from uniformly diffuse to highly directional, narrow beams. 
 
The effect and diffusion of light vary according to the beam of light. We can collect this issue in 7 ways;


Indirect 
This type of luminaire can be used to create a feeling of the height in large rooms with low ceilings. Light reflected from the ceiling and upper walls can complement structure; prevent gloomy, dark ceilings; and reduce or eliminate shadows.



 
Semi-indirect
Light reflected from the ceiling tends to soften shadows and improve brightness ratios. Luminaire brightness can be approximately equal to the brightness of the ceiling because light also is directed downward.





Direct-indirect
These luminaires provide approximately equal light to the floor and ceiling and very little light to the sides. Consequently, brightness can be low in the zone of direct glare. 





Diffuse
These fixtures provide approximately equal light in all directions. To control direct glare, diffusing enclosures should be large and lamp wattage low.





Semidirect
A small percentage of light directed upward tends to soften shadows caused by direct luminaries, like downlights. 







Direct; Wide Beam Spread
Direct fixtures can be used for focus and emphasis. To prevent high brightness ratios, ensure that sufficient illumination is provided on walls and other vertical surfaces. 







Direct;Highly concentrated Beam Spread Downlight
Beam spread depends on the reflector, lens, and position of lamp in luminaire.







Follow us on our next article “ Downlights & Glare Control ”.
 
Sources;
Architectural Lighting by M. David Egan and Victor W. Olgyay

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Sinem Erman

Sinem graduated in 2011 from Istanbul Technical University in Turkey with a BA in Interior Architecture and completed her MDes in Living and Interior Design at Domus Academy in 2013, she joined Planlux in 2018.