Colour Model (red, green, blue)
Used for the Internet, TV screens and computer monitors.
In the RGB system, the red, green and blue dots are assigned
brightness values along some scale, for example 0 to 255, where 0 is dark and
255 is bright. By listing the three values for the red, green and blue
phosphors, you can specify the exact colour that will be mixed.
Additive colours get lighter when mixed. As each component of
light is mixed in, the combination becomes a new colour. Red, green and blue
are the three additive primaries. You can mix any colour of light with
different combinations of the additive primaries. When you mix all three
together in balanced amounts, you get white.
These three primaries are the basis of the additive colour
model. It's called the RGB model, and it's usually used to create colour on
your computer display as well as other electronic devices. By mixing together
various amounts of red, green and blue light, you can make almost any colour.
The RGB colour space is a multi-coloured cube with different points showing
what colours different mixtures of red, green, and blue make.
Television screens and computer monitors make their colours by
mixing red, green and blue lights. A monitor or television screen mixes a
colour by illuminating tiny dots of red, green and blue phosphors with an
electron gun located at the back of the monitor. By illuminating each of the
dots to a different brightness, the monitor creates different colours.
Because the RGB model is only capable of producing a certain
range of colours, there are some
colours that cannot be reproduced accurately by a computer monitor. The number of colours visible on a monitor is further reduced by the
limitations of the video hardware in the computer, which may display anywhere
from just black and white up to 16.7 million colours.
HSL Colour Model
(Hue, Saturation, Luminance)
The HSL model is very similar to the RGB model. In fact, when they're
expressed mathematically, they're identical. The difference lies in how
colours are expressed numerically. The hue determines which basic colour it
is. Red, green, blue, yellow, orange, etc. are different hues. Saturation and
luminance tell more about the variations of these basic colours. Saturation
is the vividness (or "purity") of the colour, i.e., how much of the
colour's complement is mixed in. Finally, luminance refers to the
"whiteness" of the colour. It may also be termed
"brightness," "value" or "intensity."
Other models related to the HSL model are the HSB (Hue,
Saturation, brightness) and HSI (Hue, Saturation, Intensity) models. These
terms are all similar but not interchangeable.
CIE Colour Model (Commission Internationale l'eclairage)
The CIE model is a more subjective description than the others.
In 1931, the Commission Internationale l'Eclairage tested many people and
found that the sensitivity of the receptors in the eye caused certain colours
to be associated with others. The CIE colour space includes all visible
colours, whether or not they can be defined in the RGB or CMYK models. Computer printers and other devices for
displaying colour have practical limitations that prevent them from making ALL
of the visible colours. The colours that they CAN create are collectively
called the colour gamut. The CIE model is useful in part because a
printer's colour gamut can be drawn on the CIE colour space showing what
colours cannot be printed. Other colour models closely related to CIE are UCS
(Uniform Colour Space), CIELAB and CIELUV.
PANTONE Matching System See pantone