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Light Variables - colour temperature and brightness

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Blue Light

Indoor Light
Brightness levels are generally much lower indoors than outdoors. This is an important factor when lighting indoors because a different mix of photosensors is triggered in the eye, meaning we see differently indoors.

Brightness, colour temperature, and the light spectrum all play their part in helping us see and feel better.

Colour Temperature
In short, colour temperature offers us a scale to measure how ‘warm’ (yellow) or ‘cool’ (blue) a light source is. It is measured in Kelvin (abbreviated to k). The higher the number, the ‘cooler’ the light.

The image showing different colour temperatures opposite illustrates the difference between 3,000k (warm white) and 6,000k (cool white).

Colour Rendering Index (CRI)
The colour rendering index describes how closely a light source makes the colour of an object appear true to the human eye and how well subtle variations in colour shades are revealed. It is measured in %. The higher the number, the better.

As we age, the amount of light which manages to pass through the cornea, lens and aqueous fluids drops off dramatically, which is why the older eye often needs more light. By the same token, too much light will also make things worse.

Lumens (lm) - This is the measure of the total amount of visible light visible from a light source. If you are focussed on energy-efficiency, this measure matters.

Lux (lx) - A standardised unit of measurement of light intensity, which is commonly referred to as “brightness”. It measures the amount of light hitting a solid surface from a set distance. If you are performing a close task, this measure matters.

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