Colour temperature

Singapore 4th February 2012

You may have wondered what happened to me the last few days…just got sick on my last day in India. No not the Delhi-belly, just an ordinary cold or flu, not sure. Started to have a fever, coughing and so on…probably the result of a temperature shock. I had not realised that Delhi, much further up North, does not have the same temperatures as Mumbai and Goa where I was last week, so I had basically packed my same light clothing just to find temperatures in Delhi only between 9-18 degrees…I had to borrow a sweater and a windbreaker from my associate…add to that some fatigue and the recipe for a cold was there. With medicine I managed to go through my meetings on Thursday and keep the flu repressed during my overnight flight back to Singapore. Once back yesterday I basically ended up all day in bed so “sick it out”.

So what better topic then a (belated and catch up) talk about temperature, colour temperature in this case. One of the key design considerations in lighting is the choice of the colour of the light. And I don’t mean so much actual colours like Red, Green or Blue, but the various shades of white that exist. In lighting colour temperature is a characteristic of visible light and has different importance for different applications, it is always a part of my concept presentations. We talk about warm white, neutral white and cool white. In our daily lighting applications we would typify 3000K or less as being warm white (yellowish) and temperatures above 4000-5000K as cool white (bluish).

Understanding the psychology of colour is crucial to a lighting design as colours have a strong impact on our emotions, mood and senses. Cool colours are associated with (yes) cold, cool, distant, business-like as it stimulates action. Very much like sunrise early morning. Warm colours on the contrary are warm, cosy and enhances relaxation, the romantic feel of sunset.

Hence cool colours are much applied in sports, super markets, offices where you want people to go quick about their business. Warm colours are used where socialising and relaxing moods are required. The colour combinations can further be exploited to create contrasts, for instance in exteriors where buildings can be enhanced by warm light (simulating life and warmth in the building) and cool light to enhance landscape features such as trees and water elements. It is to be noted that we generally see reflections hence the colour of the light preferable should match the material finishes it reflects off.

Light & Learn 3-4: Colour temperature has been determined with the help of Planck’s law, that describes at various temperatures the colours (energy/ wavelength) emitted by a so called black body.  These black body colour hues are then compared with that of light sources to determine its colour temperature. The colour temperature is expressed in absolute temperature, the Kelvin where absolute zero is somewhere around minus 273 degree Celsius. The lower the temperature, the warmer its colour.

CIE Chromaticy diagram showing the black body locus line for light sources
Colour temperature reference scale

04. February 2012 by Martin Klaasen
Categories: Light & Learn, lighting applications, lighting design | Leave a comment

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