Spectrophotometric Protocol
Documented rules established by the International Organization for Standardization specify the spectral conditions for color measurements in the graphic arts industry. This international standard, designated as iso 13655, governs how spectrophotometers must illuminate, measure, and calculate the color values of printed paper and packaging materials. It defines the M0, M1, M2, and M3 measurement conditions to address the problems caused by optical brighteners and ink gloss.
By aligning these parameters, the standard ensures that color data can be exchanged reliably throughout the global print supply chain. This uniformity is necessary for maintaining consistent brand colors across different printing processes and substrates.
Measurement Condition
Printing operations often struggle with color variations that occur because different instruments use different light sources. The primary benefit of iso 13655 is that it defines specific lighting conditions, particularly the use of ultraviolet-controlled light in the M1 mode to match daylight. It also details the M2 mode, which uses an ultraviolet-cut filter to measure color without the influence of optical brighteners.
This structured approach allows pre-press departments and pressrooms to use the same measurement parameters, which drastically reduces the misunderstandings that occur during the color approval process. The standard provides a common language for print buyers and production plants to agree on acceptable tolerances.
Backing Standard
Substrate opacity affects color measurements because light often penetrates the paper and reflects off the underlying surface. To prevent this, iso 13655 mandates the use of a black or white backing of specified spectral reflectance during measurement. This requirement ensures that the measured color reflects only the properties of the printed sample itself rather than the tabletop or the holding fixture.
