The principle of specular gloss measurement is to measure specular reflection luminous flux (ϕs) from a surface of sample against the specified incident angle (θ). However, glass surface’s specular reflection luminous flux (ϕs) at the refractive index (n=1.567) is made as a standard under the same condition and its ratio is indicated.
Gs（θ）＝（φs／φos）×100（％）
■Basic concept of specular gloss measuring instrument
■Example of lighting and light receiving angles of optical unit
■Various modes of specular gloss measurement (from ISO 2813,JIS Z8741)
* “75° specular gloss measuring method for paper and paperboard (JIS P8142)” was the method for measuring 75° JIS glossiness by parallel light, but it was abolished on March 31, 2008. It was then switched over to the new method for measuring 75° ISO glossiness by the convergent light method (TAPPI method).
