The difference between paper whiteness, brightness and shadow

Paper brightness, paper whiteness, and shade are three of the paper selection variables that are common in print projects. However, they all play an important role in determining how the final product will look.

While it's easy to have a general idea of ​​what terms like brightness, whiteness, and shade mean, there can be quite a bit of confusion about their technical definitions and how they affect the final product's appearance.

It should be noted that although paper brightness and whiteness are somewhat similar, they are not interchangeable.

paper brightness

Luminance measures the amount of reflected blue light of a specific wavelength. Brightness is measured on a scale of 0 to 100, with the higher the number, the brighter the paper.

In other words, a 95 bright sheet reflects more light than an 85 bright sheet, and therefore appears brighter.

Using specific blue light to measure this reflection ignores longer wavelengths, including green and red. Therefore, two papers of the same brightness may visually appear very different, even though their "brightness" is the same.

Specifically, the wavelength of blue light used to measure brightness is 457 nanometers (nanometers).

paper whiteness

Brightness measures the reflection of very specific wavelengths of light, while whiteness measures the reflection of all wavelengths of light in the visible spectrum. Because of this, whiteness is more in line with our visual perception.

Therefore, there is generally a consensus that the higher the whiteness rating (also using a 0-100 scale), the whiter the paper.

Using the entire visible light spectrum, extremely white paper may appear to have a bluish tinge, depending on which light source it is viewed under.

A common measure of whiteness, D65 illuminance, stands for outdoor daylight. The standard, called CIE whiteness, was developed by the International Commission on Illumination (also referred to as CIE) headquartered in France. Of course, indoor lighting will change how white paper appears, and the variation between fluorescent and incandescent bulbs will be even greater.

paper shadow

Shadow, on the other hand, doesn't take into account any light reflections: instead, it represents the color of the paper. There are three common groups of shades of white:

• true white

• blue White

• creamy white

As mentioned above, the blue-white shade is often used on paper because it appears to be a "white" white compared to true white. These files are usually labeled "Bright White" or "High White". It has this hue because it reflects more of the blues.

The creamy white absorbs the blue reflected by the bluish white, thus giving it a yellowish appearance. True white, as the name suggests, likewise reflects the entire color spectrum, which is of course the true definition of white.

Shade selection is especially important in book printing. In addition to considering your own preferences, you also want to ensure that the shading of the paper provides visual comfort for the reader. The better choice depends a lot on the content of your book. If you are interested in book printing, please visit our book printing department to learn more.

When Brightness and Whiteness Off the Charts

If you've looked at various papers, you've probably seen brightness and whiteness levels beyond the aforementioned 100.

The 100 limit is limited to standard paper made from pulp. However, additives can be added to make the paper appear brighter or whiter.

These additives are known as optical brighteners (OBAs), and in terms of brightness, they reflect ultraviolet (or UV) light into visible light. In other words, this reflected light is more visible than the light emitted by the actual light source.

Likewise, fluorescent OPA can cause whiteness values ​​to increase above 100.

North American Paper Standard

Outside of the paper and printing industries, paper brightness is a common measurement in North America. The 0-100 scale is generally based on TAPPI Standard T451 of the Technical Association of the Pulp and Paper Industry. Outside of North America, the International Organization for Standardization's ISO standard 2469 is generally used.

As mentioned above, the standard for whiteness measurement is CIE whiteness.

Also, while white and luminance have similarities, the measurement systems used to measure each are completely separate and uncorrelated.