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correlated color temperature and color rendering index
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CCT & CRI in lighting design of spaces
Color is not a inert characteristic of any object
contd.
instead it comes with the perception of observer influenced by type of light falling
CCT and CRI are extensively used color metrics in lighting industry to explain color appearance.
Definitions of CCT
Correlated Color Temperature CCT is a measure of how warm or cool a light source appears to the human eye. It is measured in degrees Kelvin.
According to Wikipedia correlated color temperature of specific light source is the temperature of an ideal black body radiator, which radiates light of comparable hue to that of light source.
Why CCT is considered in light designing of spaces?
CCT values are needed for selection of
luminaries for lighting design of
spaces. They are intended by the
lighting industry to give specifiers a
general indication of the apparent
"warmth" or "coolness" of the light
emitted by the source.
contd.
Especially it is a prime tool for creating
themes and atmosphere for a space according
to requirement. For example, a warmer (i.e.,
lower color temperature) light is often used in
public areas to promote relaxation, while a
cooler (higher color temperature) light is used
to enhance concentration in offices (2008).
Limitation
In practice, CCT rating should be limited to white light source (not sodium sources for example) (ASSIST, 2010). Color temperature is only meaningful for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e. it does not make sense to speak of the color temperature of e.g. a green or a purple light (Wikipedia.com).
contd.
One of the potential problems of CCT is
higher color temperature yield cooler
colors of light which is subject to
confusion as opposite of the cultural
associations attributed to colors , in
which "red" is "hot", and "blue" is
"cold".
CRI
Definitions of CRI
The color rendering index CRI
according to McCamy(1992) a
quantitative measure of the ability of a
light source to reproduce the colors of
various objects faithfully in comparison
with an ideal or natural light source.
contd.
While Light Research Centre describes
color rendering index as a measure of a
light source's ability to show object
colors "realistically" or "naturally"
compared to a familiar reference
source, either incandescent light or
daylight.
CRI value
CRI values range from zero to 100. In
actual rating above 80 of a light
source is considered good for interior
setting especially retail merchandizing.
While below 70 is not good CRI
especially for retail setup.
Poor CRI Good CRI
CRI of Lamp Sources
Why CRI is considered in light designing of spaces?
CRI is needed by the architects and
interior designers for considering in
optimum selection of luminaries for
lighting design of spaces. As different
areas have different consideration
regarding color and light appearance.