On the floor, a change of one unit of brightness or opacity is a point, so a sheet that goes from 92 to 90 brightness has lost two points. The word hides big cost differences: a point of brightness near 90 is far more expensive to gain in bleaching than a point near 80, and a point of opacity on a lightweight sheet can take a large filler increase. Points are always absolute units, never percent change.
We gave up two points of opacity when they dropped the basis weight, and nobody told the printer.
Say two points, not two percent, when brightness drops from 90 to 88, or a veteran will correct you.
Also heard as
- point
Do not mix it up with
- Caliper: Board makers also use points for thickness in thousandths of an inch, which is a caliper unit, not an optical one.
Related terms
Brightness
The blue-light reflectance of pulp or paper, read at an effective wavelength of 457 nm and reported as a percentage.
Opacity
A sheet's ability to hide what lies behind it, expressed as a percentage from readings over black and white backings.
CIE whiteness
Formula-based whiteness index computed from luminance factor Y and chromaticity, under D65 or C illumination.