If you recently had to buy a lightbulb and found yourself overwhelmed by the technical terms on the back of the package, then you are in the right place.
Colour temperature, colour rendering, lumens, lumens per Watt. It can seem daunting (and believe me, it is).
This article intends to shed some light (sorry) on only one of these terms: Colour Temperature.
If that is the term that most confounded you, then Read On:-
Technically speaking, it is related to the spectral distribution of energy from a light source, treated as a perfect Black Body emitter.
Colour temperature is how ‘warm’ or ‘cold’ the light seems.
Harsh blue sunlight on a winter morning is considered to be ‘cold’ and orange-red sunlight on a summer evening is considered to be ‘warm’.
In fact the meanings have historically always been the wrong way round.
Reason is that the so-called ‘cold’ light actually contains more energy since it contains higher-frequency blue light (and also some ultraviolet).
And, the so-called ‘warmer’ light has lower-frequency (i.e. lower-energy) reds, oranges and infrared.
This all comes from the concept of Incandescence, the basis upon which the humble light bulb is built.
If you pass a current through a wire, it becomes hot, moving from a reddish colour (at lower temperatures) to blue-white colours (at higher temperatures).
Knowing the temperature of the wire filament allows us to estimate the spread of colours we can expect to see at that temperature.
So the ‘Colour Temperature’ of a light source is simply the temperature (in Kelvin, K) at which a perfect emitter of radiation (called a ‘Black Body’ in physics) would have the same colour appearance as our light source. Examples of ‘perfect emitters’ include the Sun and tungsten light bulbs.
By the way, when the light source is not a ‘perfect emitter’, the correct term is Correlated Colour Temperature (CCT). This term is used to describe most artificial sources of light, such as LEDs or fluorescent bulbs.
How we choose to light art will depend on the light-sensitivity of the materials on the object, the ambient light levels in the gallery, the reflectance of the piece, the age of your viewers, the sunblinds and filters you may have installed to block natural and artificial light sources, etc etc.
Not to mention that ‘lower’ Colour Temperature light sources will make your artwork seem yellowish and ‘higher’ Colour Temperatures will make it seem bluer.
We would always recommend a ‘neutral white’ Colour Temperature of 3500K – 4000K, depending on the light-sensitivity of the piece.
We are with you.
At ArtRatio, we have dedicated our lives to resolving this ever-so-difficult question of how to manage light in places where art and people cohabit.
Not only in buildings, but in any space where you have varying light levels throughout the year and where the objects on display do not all have the exact same requirements for conservation and exhibition.
We have a ton of stuff on this subject.
If not, drop us a line below and let us know your thoughts.