This scale measures the colour - or temperature - of the light, or, in other words, how cool or warm it is. It is a key factor in affecting the mood of a room, so its important to consider what level of kelvins you want - too high and your comfy sitting room might feel more like a corporate office. Lower kelvins generate a cosy, yellow light that work well for sitting rooms, dining rooms and bedrooms, while higher kelvins give a more energising, cool blue light which is better for activity areas such as kitchens and bathrooms. As a comparison, the old incandescent bulb registered about 2,700 on the kelvin scale and gave a warm, yellowy light, while the midday sun is 5,500k and a candle is around 1,600k.
And finally there is a measure of quality of light, the CRI or Colour Rendering Index which measures the bulb’s ability to accurately represent different colours, or ensure that a bright red tomato looks bright red and not pale or dusty red. The index works with 100 being the best representation of colour and traditional incandescent and halogen bulbs score in the high 90s, while LEDs and CFLS score more in the mid 80s. Anything above 80 is considered accurate but if you wanted to highlight a painting or pick out a particular surface detail, you might want to look for a bulb with a higher CRI value.
So, just as it is important to include different lighting options within one room, it is also important to vary the light quality within spaces, depending on the mood you want to create, the activities taking place and time of day the room will be most used. Yes, it takes a little planning but it is most definitely worth it - and can be the difference between a room feeling can’t-put-your-finger-on-it uncomfortable or perfectly right.