Fluorescent Colour Changes
‘Feel Good’ Fluorescents versus ‘standard’ fluorescents
Lower colour temperatures contain more red light and appear “warmer” whereas higher colour temperatures contain more blue light and appear ‘cooler’.
As the latest generation of ‘feel good’ fluorescent lighting including Philips' ActiViva and Osram's Lumilux Skywhite® lamps gain in popularity, the question arises — what exactly is the difference between these and 'standard' fluorescent lighting?
Colour Temperature
The light colour of a lamp depends on a combination of its colour temperature and colour rendering properties. Colour temperature is measured on the Kelvin scale. Lower colour temperatures contain more red light and appear 'warmer' whereas higher colour temperatures contain more blue light and appear 'cooler'. Standard fluorescent lamps will usually have a colour temperature of around 3,500K whereas the latest generation of 'blue sky' lamps give off a much cooler light, anywhere between 8,000K and 17,000K.
As we all know natural daylight is not a single, but a range of colours. It is this colour spectrum that allows our eyes to see in a way that we perceive to be natural and balanced. Lamps that allow colours to be reproduced similar to daylight are said to have a good 'colour rendering'. This is measured on a Colour Rendering Index (CRI) with a scale of 1 to 100 — the best scoring close to 100. The European standard EN 12464–1 requires that lamps with a CRI of less than 80Ra should not be used in rooms in which people work or stay for lengthy periods.
To see the effect of colour temperature and rendering properties, try looking at cars in a road that is solely lit by yellow sodium lamps. While there's plenty of light to see the cars, trying to identify their exact colour is nearly impossible.
What colour options are there?
There's a range of different light colours with different colour rendering properties designed to suit a variety of different applications.
It's worth remembering that manufacturers' specifications can and do vary, so it is always worth checking before ordering. For instance, Osram offers seven colour groups and three versions of lamp — Lumilux® De Luxe and Lumilux® Basic — with differing CRIs. The most popular choice for offices is triphosphor light colour 835 (white). With a colour temperature of 3,500K it strikes a balance between cool and cosy.
To create a bright and cosy atmosphere, triphosphor light colour 830/930 (warm white) is often the preferred choice with a colour temperature of 3,000K. Applications include shops, schools, meeting rooms, offices, auditoriums, etc.
The warmest light, with a colour temperature of 2,700K, is triphosphor light colour 827 (extra warm white)
The warmest light, with a colour temperature of 2,700K, is triphosphor light colour 827 (extra warm white). It's most commonly used in hotel foyers, restaurants and theatres to create a relaxing atmosphere.
To generate a cooler light there's principally two options — cool white and daylight. Triphosphor light colour 840/640/940 (cool white) lies somewhere in between daylight and incandescent light. Typically, it's a working light for factories, workshops, offices, sports halls, etc. It is also used extensively in the home.
Triphosphor light colour 860/865/954 (daylight) is ideal for where precise colour matching is required such as at dentists' practices, reprographic workshops, etc. Some manufacturers also produce a 'cool daylight' lamp aimed at the clothing retail market where colour rendering is important for customers.
Finally, there's the latest generation of white light lamps — Lumilux Skywhite® from Osram (light colour 880) and ActiViva from Philips. These lamps emit a large amount of blue light and arguably are the closest possible to real daylight. ActiViva has a colour temperature of 17,000K and CRI of around 98. Both give offices, classrooms, libraries and shops a breath of fresh air.
The choice, as they say, is yours.
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