Paper Whiteness, Brightness, Shade
Professional printers and designers are well-versed in the nuanced concepts of paper whiteness and brightness, which play critical roles in determining the quality and suitability of paper for specific projects. However, for many outside the industry, these terms might seem like jargon, often making it challenging to understand their importance or to make informed decisions when selecting paper.
The distinction between paper whiteness and brightness is akin to other paper-related variations, such as paper size and weight, which also differ in standard usage around the world. Internationally, the concept of Whiteness is more widely utilized, governed by standards set by the CIE (Commission Internationale de l’Eclairage or International Commission on Illumination). This measure of whiteness aims to reflect how closely paper approximates pure white, influencing how colors printed on it are perceived.
In contrast, in the United States, Brightness is the predominant measure, as defined by TAPPI (Technical Association of the Pulp and Paper Industry). Brightness refers to the percentage of blue light (with a wavelength of 457 nanometers) that a paper reflects. This measurement indicates how much light a paper can reflect and is a critical factor in enhancing the readability and clarity of the printed text or images, particularly for high-contrast uses such as in book printing or academic publications.
Another critical term in the industry is “Shade,” which universally refers to the color of the paper itself, measured using the CIE LAB model (also known more formally as CIE L*, a*, b*). This model quantifies the exact color of the paper in a way that correlates well with human vision, accounting for lightness (L*), green to red component (a*), and blue to yellow component (b*). This measurement is crucial because the paper’s shade can significantly affect the appearance of the printed colors, impacting the overall aesthetic of a printed piece.
Understanding these terms can greatly assist non-professionals in selecting the right type of paper for their needs, whether for professional presentations, art reproductions, or everyday printing. By considering the whiteness, brightness, and shade of paper, consumers can better anticipate how their documents will look in various lighting conditions and how true to color their printed images will appear. This knowledge is especially important when striving for high accuracy in color reproduction in fields such as photography and fine art printing, where the subtle nuances of color and light are paramount.
Paper Whiteness
Paper whiteness is a crucial factor in the printing and paper industries, reflecting how manufacturers and designers think about the color and appearance of paper under various lighting conditions. The CIE (Commission Internationale de l’Eclairage or International Commission on Illumination) whiteness measure provides a standardized approach to evaluating paper whiteness, emphasizing its performance under a specific lighting condition known as D65 illumination. This standard is meant to simulate natural outdoor daylight and is used to measure the light that paper reflects across the visible spectrum.
For materials that perfectly reflect all incident light without any fluorescence, the CIE whiteness value would theoretically be 100. However, most commercial ‘white’ papers typically exhibit CIE whiteness values ranging between 130 and 170. This increased range is primarily due to the use of Optical Brightening Agents (OBAs). OBAs are special additives used in paper manufacturing to enhance brightness and whiteness. They work by absorbing ultraviolet light—which is invisible to the human eye—and re-emitting it as visible light. This process boosts the overall brightness and whiteness of the paper as perceived by human eyes, making the paper appear more vibrant under certain lighting conditions.
However, the effect of OBAs can vary significantly depending on the lighting under which the paper is viewed. Paper that contains a high amount of OBAs might look exceptionally bright in sunlight or under other UV-rich lights but could appear less vibrant under indoor lighting conditions that have limited ultraviolet light. Conversely, paper with a good, naturally white base but fewer OBAs will maintain more consistent whiteness across different lighting conditions but might not have that extra ‘pop’ under UV light.
This variability in appearance under different lighting conditions is known as metamerism. Metamerism can be particularly challenging when assembling documents from various sources or papers, as the different papers may appear to match under one light but not another. This effect can impact the overall cohesion and aesthetic of printed materials, especially in professional or artistic settings where visual consistency is key.
When preparing documents, especially those intended for professional presentation or distribution, it’s advisable to select paper types carefully. Ideally, all components of a document should be printed on the same type of paper to minimize variations in appearance under different lighting conditions. This consistency helps ensure that the document conveys the intended visual message accurately and effectively, regardless of where or under what lighting conditions it is viewed.
Paper Brightness
Paper brightness is an important attribute in the paper industry, particularly in contexts where the clarity and vibrancy of printed materials are critical. Brightness specifically refers to the reflectance of a specific type of blue light and is a measure standardized by TAPPI (Technical Association of the Pulp and Paper Industry). A typical example can be seen in a ream of paper marked with a “98 brightness,” indicating a high degree of brightness that directly influences how vivid the paper appears when used for printing.
TAPPI defines brightness as the reflectance of blue light at a wavelength of 457 nanometers, within a bandwidth of 44 nanometers. This measure specifically assesses how much light a paper reflects, which is crucial for applications requiring sharp, clear print results such as in publishing or high-quality office printing. It is common for the packaging of such paper to prominently display the brightness value, for instance, “98,” to inform consumers about the paper’s suitability for their specific needs, emphasizing its high reflectance capability.
In addition to TAPPI’s standards, the ISO (International Organization for Standardization) also has a standard for measuring brightness, detailed in ISO 2469 (Paper, board, and pulps—Measurement of diffuse radiance factor). However, this ISO standard is less frequently used compared to the TAPPI measurement in the United States and the CIE whiteness scale internationally. The CIE scale is broader, incorporating more aspects of how paper reflects light, making it a more comprehensive measure in global contexts.
Brightness values exceeding 100, often seen in measurements, suggest that the paper reflects more light than is shone upon it. This phenomenon is largely attributable to the presence of Optical Brightening Agents (OBAs). These agents are incorporated into the paper to enhance its visual perception under certain lighting conditions. OBAs work by absorbing ultraviolet light and re-emitting it as visible light, effectively making the paper appear brighter to the human eye.
However, it’s essential to note that while OBAs can significantly increase a paper’s brightness under UV-rich light, such as sunlight, they might contribute less under lighting with little to no ultraviolet light, such as some indoor environments. Typically, TAPPI brightness values, ranging from about 110 to 120, are somewhat lower than the CIE whiteness values, which can go higher due to the broader spectrum of light considered in the CIE measure.
Understanding these measurements—brightness and whiteness—is crucial for making informed decisions about paper selection, particularly in professional settings where the visual quality of printed materials can have a substantial impact. Knowing whether a paper’s brightness or whiteness aligns with the project’s requirements can help in selecting the most suitable paper type, thereby enhancing the final output’s effectiveness and aesthetic appeal.
Paper Shade
When selecting paper, the specific shade can significantly influence the appearance and readability of printed materials. Paper does not typically achieve a “true white,” which would involve reflecting all colors of the spectrum equally. Instead, most papers exhibit subtle tints, such as bluish or creamy hues, which affect how they interact with light and color.
The term “paper shade” refers to these subtle color differences. For example, a ream of paper described as having a “cream tinge” will exhibit a warmer, slightly yellowish appearance. This effect arises because cream-tinged paper absorbs more of the blue light and reflects longer wavelengths like red and yellow. Conversely, a “blue white” shade of paper reflects more blue light while absorbing some red and green light, giving it a cooler, crisper appearance.
The most precise way to measure these variations in paper color is by using the CIE LAB model, also known as CIE L*, a*, b*. This color model is highly regarded because it encompasses the entire color space, unlike other models such as RGB (used for digital displays) or CMYK (used in color printing), which only cover subsets of the LAB space. In the CIE LAB model:
- L* represents lightness,
- A* measures the red to green spectrum,
- B* measures the blue to yellow spectrum.
This comprehensive approach allows for a precise description of paper shade, crucial for ensuring consistency and achieving the desired visual effects in printed materials.
Choosing the right paper shade can have practical implications depending on the intended use of the paper:
- Blue white shades are often preferred for short documents, such as office reports or academic papers, because they offer high contrast with black ink, enhancing readability. The crispness of blue white paper makes the black text stand out, facilitating quick reading and note-taking.
- Cream white shades are favored for books or long reads. The softer, warmer tone of cream paper reduces glare, which can lessen eye strain during extended periods of reading. This makes it ideal for novels, textbooks, and other lengthy printed works.
- True white shades are best suited for printing documents that contain vibrant, warm colors like red, orange, and yellow. The neutrality of true white paper ensures that these colors appear more vivid and are not influenced by the paper’s own hue.
Understanding these nuances in paper shade can help consumers, designers, and printers make informed choices, aligning the paper’s characteristics with the specific needs of the project to optimize aesthetic appeal and reader comfort.
