Paper Standards Measur Umschlag - Sappi Mobile

CIE-Whiteness ISO 2470
Whiteness is a subjectively perceived property. Most people
consider that it increases when the material has a slightly
blue tone. It is thus clear that whiteness in some way is an
aspect of colour perception, and that any measurement of
whiteness must be based on colour management.
Shade (colour) ISO 5631
Shade of a paper is the colour of a paper. The colour is described
as blue, green, yellow or red or as a mixture of these
colours. The colour can be described according to intensity
and saturation. There are several different systems in use,
but most common for the paper industry is the CIE L* a* b*.
Opacity ISO 2471
The opacity is a measurement for the light transparency
degree of the paper, expressed in a percentage in relation to
the reflected light. Paper which lets a lot of light through is
transparent; paper which lets less light through is opaque.
The higher the value, the more opaque the paper is.
Metamerism
Metamerism is the condition in which two colours can
appear identical under certain light sources but exhibit clear
differences in other light sources. This occurs because the
reflective/reflection curves of the metameric colours are not
the same/alike over the whole spectrum.
Fluorescence
If a colour becomes more optically intensive under a certain
light source it is due to the effect of fluorescence. This
occurs when parts of the incident light are reflected in other
wavelengths. The impact of fluorescence is shown by the
optical brighteners used in many papers as they convert UV
light into visible light.
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Yellowing DIN 6167
Degree of yellowing / discolouration of paper exposed to daylight
or heat, after a specified period of time. A test piece is
exposed for a specified time to UV light or heat. Colour measurements
at specific time intervals describe the yellowing /
discolouration. The degree of yellowing is expressed in a yellowing
number.
Elrepho