When people talk about the colour reproduction of lights, they are typically referring to the properties of the light that's produced. A particular globe may produce light that is 'warm', 'cool', 'daylight' or 'full spectrum' – and that’s not including actual colour variations such as red, green, blue or black.
Colour temperature refers to how warm or cool the light appears to be. A cool light, for example, gives off a blueish-white light, while a warm light will give off a light that is yellowish, orange or red. A daylight globe, on the other hand, gives off a strong, white light. Typical residential light bulbs are normally either cool or warm, depending on where in the home they are, and what they're being used for.
How to choose between warm and cool lights
Cool lights improve our ability to see contrasts, and are typically favoured for use in kitchens, bathrooms, laundries and the like. Warm lights are more relaxing and inviting, and are designed to mimic the light created by fire. These types of globes are favoured for living areas, hallways and foyers, and bedrooms.
Having said that, your furniture can play a role in helping you decide on whether you need cool or warm lights too. Variations of lighting colour can affect the way you see the furnishings and fixtures in your home. If you have ‘warmer’ coloured furniture that is red or brown, you should be using ‘warm’ white bulbs. If you have brighter furniture you should be using ‘cool’ white bulbs. If you have a mix of both, use bulbs that produce light in the 3,500K range.
How to identify colour temperatures
Colour temperature is measured in Kelvins. A colour temperature of 4,100K typically indicates a ‘cool’ white colouring, and a ‘warm’ bulb is typically around 3,000K. There are also what are known as ‘full spectrum’ bulbs, which feature a colour temperature of 5,000K. They are designed to make all colours stand out because of their bright, white light. Even brighter, bulbs that are 5,600K are called ‘daylight’ bulbs because of the clean, crisp light they produce.
The colour rendering index (CRI)
Unfortunately though, a colour temperature rating is not always an effective indication of how a light will truly work. Two different bulbs that have the same colour temperature can easily produce vastly different looks on coloured objects. To avoid this though, there is a way to measure how well a bulb can render true colouration: the colour rendering index.
The colour rendering index (sometimes called the colour rendition index) is a scale system used to identify how well a light can reproduce colours. This works by providing a rating for the bulb between 0 and 100, where 100 represents perfect, natural colour reproduction.