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The most common method of generating colour by
the additive system is visual display units, such as computer display screens
and television screens. Visual display screens are composed of individual
dots, which, at normal viewing distances, are too small to be seen and the
picture appears continuous. |
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The steps in the conversion of the RGB codes in an electronic
image file to the brightness (luminance) of the light emitted by the display
screen are described. The power law factor, white point for each of the
standard types of display systems are explained. |
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Four-colour printing is the method used for the reproduction
of coloured illustrations in many newspapers, magazines and on packaging
materials. The technique is based on the trichromatic nature of human colour
vision in that, under normal viewing conditions, there are three signals
arising from the cone shaped sensors in the retinal layer of the eye |
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The steps in the conversion of the intended colour of a printed
area (XYZ) to the relative areas of the substrate covered by dots of cyan,
yellow and magenta ink (CYM) is not straightforward. It is simpler to consider
the reverse transformation, taking a set of known values for CYM and determining
the colour of the print (XYZ). |
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The challenge of colour image reproduction is to capture
a scene and then to display or to print the image with the highest possible
fidelity to the appearance of the original scene. At its simplest the reproduction
chain of has four stages: (scene capture) – (image storage) –
(image display and editing) – (copy production)
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Reflection density is widely used for quality and process
control within the graphic arts industry. Once the half-tone characteristics
of a visually acceptable print is established, densitometry offers a way
of assessing the properties of a print using parameters that are directly
related to the half?tone process. |
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