Sheen_Catalogue AW.indd

Appearance
1.0
Colour
The human eye is capable of differentiating
several million colours, despite this
subjective visual evaluation, when used
for quality control purposes, is no longer
preferred as it suffers from a lack of
real quantifiable data and inconsistent
documentation. Since the early 1930’s
many scientific measuring techniques
have been developed by National
Standards Organisations, among them
the CIE (International Committee of Light),
based on a logical numeric scaling where
physical parameters and calculations have
been clearly defined, universally accepted
and adopted. As a result, many methods
are today perfectly proven, and governed
by major standards such as ASTM, BS,
DIN, or ISO etc.
02
Colour vision
Colour is described as an interaction of:
light sources – objects – human eyes.
Light source
depending on their type and physical characteristics, light
sources influence the perception of colours.
for industrial purposes, major light sources - or illuminants
- are standardised :
a : incandescent lamp
C : north-sky daylight
d (65) : daylight - widely used
f (various) : fluorescent lamp
due to metamerism, colours identical under one light source
may show differences under others.
Object
depending on their type, their surface condition, glossy or
matt finish, opacity, materials can reflect and absorb light
differently, thus influencing the colour perception.
for these reasons, samples and measuring conditions
should be defined and carefully prepared by the user.
for paints and inks, the use of an automatic precision film
applicator provides perfectly reliable samples.
Observer
Human eyes can see within a spectrum of approx. 400 and
700 nm. Colour vision is transmitted by the eye via a network
of receptors, basically sensitive to 3 colours, standardised
as tristimulus values:
X = red - Y = Green - Z = Blue
based on a 2° or 10° observation spot.
These values constitute the basis for the calculation of many
measuring systems, from Chromaticity Coordinates to the
most widely used Cielab colour space.