wissner-bosserhoff Carisma Gebrauchsanweisung Seite 114

APPENDIX E: METAMERISM – THE APPARENT SAMENESS OF SURFACES AND
DÉCORS
"Metamerism"
Two colours appear to be identical only under a specific type of light. If the light changes,
differentiations occur, due to the spectral properties of the pigments, colours and materials
used. A green coat bought in a shop may suddenly turn brown out on the street, but the
green trousers have remained green. To look closely at critical colours in clothes, people
often go into daylight, but since this is rather problematic formatching print and material
colours, daylight/ daylight-similar light D65 is used.
This is therefore a phenomenon involving the conditional similarity of colours. Two colours
or more appear to be identical only under a specific type of light (e.g. a neon light) and
otherwise display differences due to their spectral properties (e.g. the pigments and paint
materials used) under any other lighting.
sunlight has a different effect than in yellow sunlight. Metamerism is the colour difference
between two or more colours in materials changeable by light.
Particularly when different materials, different colouring and printing techniques are used,
slight differences in colour are almost bound to occur under different lighting conditions
(neon effect, shop lighting effect or exhibition effect are terms referring to such typical phe-
nomena).
For colour comparisons of unidécors, colorimetry is a useful instrument. A so-called meta-
merism index is used as a comparative value between two samples. The metamerism index
is the Delta E value in the CIE L*a*b system under two light sources in each case – usually
from a daylight source (C, D50, D60) to an artificial light source (A). Combined colour and
gloss-measuring instruments are used for this purpose.
For wood décor, structural décor and pattern prints, on the other hand, a visual assessment
must be made, on a pattern repeat, since a purely metrological colour comparison mea-
surement cannot be practically implemented. It is important to reach an interdisciplinary
highly individual.
The so-called pattern repeat is the smallest separate unit of a pattern. If a pattern (e.g. for
print foils or materials) is therefore composed of several small parts, a single part is called
a pattern repeat (e.g. a print section of 1.5 m in length, after which the basic pattern is
repeated).
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