What Is the Difference Between Whiteness and Brightness?
It was one of those “a picture is worth a thousand words” moments. It all started off innocently enough.
“So is ‘brightness’ a guide for white paper worldwide?” Matthew was curious and rightfully so. He was fairly new to the world of commercial printing, eager to get it right, and wanted to learn. Kudos to him. What startled us, though, was his follow-up question: “So what does brightness tell me about the shade of the paper?”
Try as I may, my verbal explanations did not make too much sense to him…or so I suspected. So I rummaged through my hard drive and came up with a simple chart about whiteness versus brightness that I use when giving talks and teaching classes. And yep, the penny dropped after I emailed it to Matthew…
Confused about Whiteness and Brightness?
Brightness is a traditional measure that still appears on most packaging in the United States. The TAPPI standard (GE brightness) measures the ability of a paper to reflect blue light. On a scale of 0 to 100, the higher the number, the brighter the sheet.
Whiteness measures paper in the same way the eye sees it. Light is actually made up of all colors combined. When light strikes an object, the object absorbs some colors and reflects others. (Think of the blue ocean…that is not really blue, is it?)
CIE Whiteness, developed by the France-based International Commission on Illumination (aka CIE), is the most commonly used whiteness index. It normally refers to measurements made under D65 illumination, which is a standard representation of outdoor daylight. For a perfect reflecting, nonfluorescent white material, the CIE Whiteness would be 100. Papers containing fluorescent additives such as Optical Brightening Agents (OBA) will also measure well above 100.
Whiteness is really the absence of color. The CIE index has been devised so that most people will agree that the higher the whiteness, the whiter the material.