The M FactorWhat Does It Mean Successful Color Management (Page 1 / 5) White Paper

The M Factor…What Does It Mean?

Successful Color Management of Papers with Optical Brighteners

Raymond Cheydleur, Global OEM Technical Manager, X-Rite Inc.

Kevin O’Connor, Color Consultant

White Paper

Many modern printing and proofing papers contain Optical Brightening Agents [OBA]. These agents are added to enhance the

brightness of the papers and improve the appearance of the printed product. The presence of these agents in contemporary papers

creates challenges for successful color management, so new standards have been defined to help manage and communicate color for

papers containing these brightening agents.

Introduction

OBAs operate through the process of fluorescence. They absorb invisible ultraviolet

(UV) radiation at wavelengths below 400 nanometers (nm) and, through an electro-

physical change, emit light mostly in the blue end of the visible spectrum at about 400

to 450 nm. When this light is emitted from papers using brightening agents, they are

perceived as having a color that is “whiter than white,” since the observed light from

the paper will be the total of the reflected and emitted (due to fluorescence) light when

illuminated by a source containing a large UV component. You can often see this effect

if you illuminate a paper containing brightening agents with an ultraviolet light source,

such as a “black” light.

The perceived color of a piece printed on a substrate containing OBAs will look

different, depending whether the light source used to view the print contains UV or not.

Older graphic arts measurement standards (except for density standards) specified

D50. It was assumed that all substrates would measure the same using a D50

illuminant, and OBA content was not a concern. In practice, colors viewed under real

viewing conditions containing UV sometimes were notably mismatched, and failed to

meet expectations. These mismatches created serious challenges for people trying to

measure and manage color consistency in a variety of workflows.

New Technologies, New Papers and New Standards

New illumination sources, including light emitting diodes [LED], allow handheld color measurement instruments to measure with

well-defined and controlled UV illumination components. To ensure consistency, new illumination sources and new substrates require

new instrument and measurement standards for defining and measuring the relative UV content, and thus the degree of fluorescence

of substrates containing OBAs. Defining and controlling the emitted UV component of the measuring device’s illumination is essential to

defining standard ways to measure and manage color printed on OBA-enhanced substrates.

X-Rite has always been at the forefront of advocating and helping to design standards for our evolving industry, and has continually

advocated the concept of printing to standards. Factors driving this evolution include technology advancements, increasing distribution

of information across different media, and the need to improve the efficiency, productivity and profitability of print providers and their

supply chain partners.

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Grand Rapids, Michigan USA • +1 800 248 9748 • +1 616 803 2100 • xrite.com