What is Paper Brightness (was RE: defining media white)
What is Paper Brightness (was RE: defining media white)
- Subject: What is Paper Brightness (was RE: defining media white)
- From: Scott Olswold <email@hidden>
- Date: Tue, 2 Oct 2001 13:38:06 -0400
Tony and all,
Brightness for pulp and paper is measured in ISO brightness ("ISO
Brightness" is the amount of light reflected from the surface of a sheet as
compared to the amount of blue light--457-nanometers wavelength--that
strikes the surface), which is measured as a percentage of absolute
whiteness. Unbleached softwood sulphate pulp has a brightness of about 26%
ISO. Sulfite pulp is much brighter, 60--65% ISO. Bleached pulp have
brightness values from 70% to more than 90% ISO. Newsprint has a brightness
of 65--70% ISO. Printing and writing papers have brightness values between
85 and 90% ISO and have to be made from highly bleached pulp.
I believe the light source is at a 45 degree angle to the stock, while the
measuring instrument is at a 90 degree position (relative to the surface).
Scott Olswold
Senior Systems Support Engineer
Danka Office Imaging
MCSE, CNA 5, A+, Network+, Adobe Certified Expert (PageMaker and Photoshop)