The appearance of paper can be judged on different parameters, like, whiteness, brightness, texture and colour. All these factors play a major role in determining the quality of the paper. Three terms are commonly used brightness, whiteness and shade. For a layman, this can be quite confusing. In this post, we would try to put some spotlight on these three terms.
It should be noted that though paper brightness and whiteness are somewhat similar, they are not interchangeable.
Whiteness and brightness are often confused and sometimes used interchangeably. But what important to note is that they both have different meaning and cannot be interchanged.
Brightness of Paper
In reference to white colour, it is related to the specific wavelength of blue light. It is the amount of reflectance of a specific wavelength of blue light. It is measured on the scale of 1-100. Higher the value means higher is the reflection of light that makes it appear brighter. Two papers with same brightness can appear visually different. The reason behind is the usage of blue light for measuring the brightness. This discards the longer wavelength including red and green. Specifically, the blue light used to measure brightness has a wavelength of 457 nanometers (nm)
Whiteness of Paper
It is the measurement of the reflection of light of all wavelength across the visible spectrum. It is again measured between 0-100. Higher the value is whiter the paper is. While measuring the whiteness, the light source under which it is being measured. White paper tends to reflect blue tint considering the nature of observing light. The most commonly used observation light source is D65. For paper colour measurement and comparison, different instruments like spectrophotometer and colour viewing booth are used.
Shade of Paper
The shade of paper simply represents the colour of the paper. The wavelength of light reflected from the visible spectrum by the surface is the shade of the paper. It is very different from the brightness and whiteness of the paper and cannot be measured on the scale of 0-100. You simply need colour measurement devices to quantify the shade. Colour managers are proficient in understanding the terminology and notation of the colour in the form of L*a*b and ?E. Based on these observations, their further applications are decided.
Testronix is the leading manufacturer and supplier of paper colour measurement devices. Apart from brightness, whiteness and shade, some smart devices are capable of measuring the gloss of the paper, required for high-end applications.