Whiteness, there are so many!

Whiteness is an index to evaluate the whiteness of white objects. Different industries have different whiteness indexes and expression habits;

Common whiteness formulas are divided into:

1) Single-band whiteness formula, such as blue light whiteness

2) Multi-band whiteness formula, such as Taube formula

3) Whiteness formula expressed in L or Y and chromatic purity, such as MacAdam formula

4) Color difference related whiteness formula Such as Hunter whiteness formula

5) CIE whiteness formula

Although the formula is the same, there will be different light sources and test geometry requirements in different industry standards, which are explained below:

Blue light whiteness:

Also known as R457 whiteness, the percentage of blue light reflected by an object at 457nm (half-wave width 44nm), mostly used in the papermaking industry, and in some standards there are other nicknames such as ISO brightness, D65 brightness, Tappi brightness, GE brightness, etc.;

Involved standards:

ISO2470-2, D65 light source, d/0 geometry, also known as D65 brightness;

TAPPI T452, C light source, 45/0 geometry, also known as Tappi brightness; also known as GE brightness;

TAPPI T525, =C light source, d/0 geometry, also known as Tappi brightness; 

GB8940.1, D65 light source, 45/0 geometry (has been replaced by 7973)

GB2913, D65 light source

Similar standards:

GB/T7974, D65, d/0 geometry; diffuse reflection factor of (457±0.5) nm, also known as brightness

GB/T7973, D65, d/0 geometry; diffuse reflection factor of (457±0.5) nm, also known as brightness

Related parameters: Fluorescent brightness, the difference between R457 measured under 420nm filtering conditions and R457 measured under D65 conditions;

CIE whiteness:

Developed from Ganz whiteness, it is used in many industries such as papermaking, printing, textiles, plastics, etc. Its formula refers to the relevant WeChat after the article, where the light tint index must be between ±3 (or -4<Tint<2), the CIE whiteness value is meaningful, otherwise it is invalid.

Standards involved:

ISO11476, C/2, d/0 geometry; ISO11475, D65/10, d/0 geometry;

GB/T22879 is equivalent to ISO11476, C/2, d/0 geometry;

GB/T22880 Equivalent to ISO11475, D65/10, d/0 geometry;

Other whiteness formulas and conditions

Berger whiteness: proposed by A. Berger of Bayer Company in Germany in 1959, used in papermaking and textile industries;

Light source C/2, geometry 45/0

Stenssby whiteness: mainly used in detergent industry, also used in papermaking industry in small quantities; light source C/2, geometry 45/0 and d/8 are both acceptable

Ganz whiteness: In the 1960s, colorimeter E. Ganz proposed three whiteness formulas with different weighting factors, namely neutral white, greenish white and reddish white, and recommended using D65 illumination body, which was later adopted and developed by CIE and called CIE whiteness.

Hunter whiteness: Hunter whiteness formula proposed by Hunter based on Hunter Lab color space.