Pass / Fail; Brightness T (Tappi 452); Yellowness Cie - Techkon SpectroDens Manual

Manual TECHKON SpectroDens

Brightness T (TAPPI 452)

Like whiteness, paper brightness is also a measurement of the amount of light reflected from
paper. Unlike whiteness, it is focused on a narrow wavelength of blue light as opposed to all
wavelengths in the spectrum. The higher the number on the brightness scale, the more light a
particular sheet reflects. Brightness is just one part of the equation when determining the visual
aspects of paper. Two sheets with identical brightness can look drastically different because
shade and whiteness are not taken into account.
In general, there are two measurement systems that are widely used for determining paper
brightness. One (used in North America) is the TAPPI scale. The other (used primarily in other
parts of the world) is the ISO system. Some papers can have a rating higher than 100 on the
brightness scale. This is due to optical brightening agents present in the paper. When these are
applied, the paper can actually reflect more light than is coming from the source. An easy way to
remember this is the brighter, the whiter.

Yellowness CIE

Yellowness is the degree that the color of a surface is shifted from preferred white (or colorless)
towards yellow.

PASS / FAIL

The PASS / FAIL function shows at a glance if a measured sample is in or out a set toler-
ance compared to a reference value.
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First, set the allowable limits of the ∆E*-toler-
ance.
Select in the menu section of the measure-
ment conditions the item PASS / FAIL toler-
ance and edit the desired tolerance value by
pressing the arrow buttons.
Every sample measurement is compared to
the reference.
If the color distance is within the set tolerance
(in this case 1.24 < 3.0), PASS will be displayed.
For out of tolerance measurements, accord-
ingly FAIL will be shown accompanied by an
acoustic signal of three short beeps.