This guide will explain colour temperature and Colour Rendering Index (
CRI),
which will help you to choose which energy saver lamps or fluorescent tube lamps
to buy.
Colour Temperature
This is a measure of how warm or cool the light given off by a fluorescent lamp
appears, with warmer colours having a yellowish tinge and colder colours appearing
a lot brighter. What confuses some people is that the warmer a colour is, the colder
its colour temperature is. This is because something which is red hot is actually
colder than something which is white hot (which makes sense when you think about
it) but psychologically the bluish white object seems colder as we associate blue
with cold.
Here at The Light Online Australia all our offices and work areas are fitted with 6500k lamps.
It helps provide the staff with better light levels and it is deemed to appear a
much nicer atmosphere.
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| Light Online Australia - Colour Temperature Index |
Colour temperature is measured on the Kelvin (K) scale, which uses the same units
as the Celsius or Centigrade scale, but starts at absolute zero (-273 degrees Celsius).
It is called colour temperature as is derived from the colours of light emited when
a body of carbon is heated to different temperatures. If you were to heat it to
2700K it would glow yellowish-white, and if you heated it to 5400-6500K it would
glow bluish-white.
A warm white lamp similar to an incandescent bulb, including halogen, has a colour
temperature of around 2700K, and gives off light with a yellowish quality, while
5000-6500K represents a bluish white colour as shown in the colour guide.
The most common colour temperatures available are as follows:
2700K is classed as
extra warm white and is common in
many of the lamps available from supermarkets, DIY sheds and the free ones given
away by energy companies. However, this colour has done more damage to the use of
CFLi’s due to many retailers selling inferior quality items causing headaches, poor
lighting and in some cases short life. At the
Light Online Australia we only stock reputable
quality lamps with this rating.
3000K is still classified as
warm white, but is slightly
colder than 2700K and mimics a halogen lamp. Therefore
3000K fluorescent tubes are often used in
kitchens which are decorated in white or silver metallic to give a clean feel. We
have
Deluxlite branded compact fluorescents in 3000k.
3500K is bulk
standard white and has been around for over
70 years. Popular in warehouses, corridors, offices and many other applications
where people are situated. Half our warehouse is in white and the other half in
Daylight. It looks strange but it’s used in many editorials.
4000K is classed as
cool white that is often used in office
buildings, and you might consider it for a home office to give a more professional
feel. It will also appear brighter that White and warm white.
5400-6500K lamps are often branded as '
daylight lamps', having a similar quality of light
to a hot summer's day with a blue sky. This is a very cold light that would not
usually be used in the home, but may be helpful for people with Seasonal Affective
Disorder. (
SAD)
Colour Rendering Index (CRI)
This is a measure of how realistic colours look when they are lit by a lamp. A standard
incandescent bulb scores 100% as it produces the full spectrum of colours and therefore
has perfect colour rendering.
Fluorescent lamps have a lower CRI because they do not produce the full spectrum
of light. Good quality '
triphosphorfluorescents' use three phosphors to give off red, green and blue light.
This tricks your eyes into thinking they are seeing white, in much the same way
as a TV screen works. If you want colours to look good, you need to choose a fluorescent
lamp with a CRI of 80% or higher - this will be fine for everyday use. Specialist
fluorescents are available with a CRI higher than 90%, but these are slightly less
efficient and are usually only used by professionals such as graphic designers or
artists.
You should avoid buying tubes for the home if they do not have a CRI rating of at
least 80%, as they may be cheap tubes intended for office buildings. These only
use a single phosphor that leaves large gaps in the spectrum of light. They have
a CRI as low as 50%, which tends to give people's skin a sickly look, and colours
just don't look right. They are also now banned under EU regulations. These give
energy saver bulbs a bad name, but are greatly out-performed by modern, household
fluorescents with a high CRI.
Perceptions of fluorescent energy saver lamps
People often complain that they do not like fluorescent energy saving lamps because
of the colour they produce. This is because they buy discounted 2700k lamps from
their supermarket or receive free energy saving lamps from their Energy Company;
free ones that are paid for out of their energy bill! These 'free' lamps help energy
companies hit their 'carbon reduction targets' but of course don’t even have to
be installed! Nothing in life is free.
