Correlated Colour Temperature

A lot of people think that the colour temperature relates to the brightness of light output – this is entirely false. The colour temperature relates solely to the colour of the light and nothing else. A light with higher Kelvin can have less light output than one with lower Kelvin.

The reason for this is that we use Correlated Colour Temperature (CCT) to describe colour of light, rather than the true Kelvin scale that relates to light output based on heat. Extended explanation: Show | Hide

Colour Temperature is measured in Kelvins. The Kelvin scale is a thermodynamic temperature scale based on the principle that a black body radiator will begin to emit light when heated, the colour of which is dependent on the temperature of the radiator (think a blacksmith heating a piece of steel so it glows red). As the temperature increases, the colour changes from red, yellow, white through to blue hues (blue being the hottest). To give an indication, 3500 Kelvin is equivalent to 3,226.8 degrees Celsius and 6000 Kelvin is 5,726.8 degrees Celsius. To give you a reference point, orange flames in a fire are around 1200 degrees Celsius.
In lighting, innovative new technologies have created globes that run much cooler (such as HID and LED) than in older technology. We therefore talk about the light output as having a Correlated Colour Temperature or CCT; that is, the colour that human colour perception matches most closely to the true Kelvin scale. In some light sources (such as an incandescent light bulb) the light that is emitted is thermal in origin and therefore has about the same actual colour temperature and CCT.

1700K
1850K
2700-3300K
3500K            
4100K            
5000K            
5500-6000K
6500K            

The short of it is, the lower the Kelvin, the light appears more yellow,
the higher the Kelvin, the light appears more blue.
At 6000 Kelvin (daylight), the light appears cool white with a slight blue halo.

Quartz halogen bulbs at 100 Watts are rated at 3500K, which is in the
yellow end of the colour temperature spectrum.
HID systems typically come in either 4300K or 6000K.
4300K is whiter than a QH globe, but still sits just inside the yellow spectrum. 6000K is considered to be cool white and close to natural daylight.

Now that you’ve got a concept of colour temperature and the Kelvin rating of the two globe types in Xray Vision driving lights, we can show you how to increase the Kelvin output of the light by using blue filter lenses.

The light colour theory is that human beings have evolved to live in a world that is filled with 6000K daylight. This is the colour we perceive as cool white, it is what our eyes adjust most easily to see more detail, and also allows our eyes to relax and assist concentration in normal day-to-day activities. We believe, therefore, it appropriate for people to use driving lights that emulate the colour of daylight, meaning they can drive under more natural lighting conditions.

Blue lenses on QH driving lights take the Kelvin from 3500K up to 4000K, and on HID driving lights with 6000K globes from 6000K up to about 6300K.

The blue lens on Xray Vision driving lights takes some of the yellow spectrum out of the light being emitted, giving the user a cleaner, whiter light on the road. There is a very slight loss in light output (about 5%), so people wanting the maximum light output will still prefer the clear, but most will see the benefit as shown in the two photographs.

The other advantage is higher Kelvin gives greater clarity in poor visibility situations such as mist, rain or fog.

Blue lenses on HID globes aren’t really necessary as the light is already cool white, however some people prefer the icy blue-white light while others like the physical appearance of the blue lenses when they’re fitted to their vehicle.

Blue or clear lenses are available right across the range of Xray Vision driving lights (all models and beam patterns) for no extra cost – representing great value.