572nm Opacity is the characteristic ability of a material to hide from view a non-active backing material. When reading a book, one prefers to read one page at a time, rather than read all of the pages at once.

Each page must have sufficient opacity to obscure the printing on the subsequent pages. If the intended use of the paper is to allow the objects placed behind it to be seen, such as glassine, then transmittance measurements should be utilized rather than opacity measurements. To simulate viewing conditions a ratio means of opacity measurement has been adopted by the paper industry and has been used for many years. ISO (Printing Opacity) = R 0 / R ∞. ISO 2471 specifies a response of Y C, which has an effective wavelength of 557 nm.

In TAPPI T425, the specified response is Y A, which has an effective wavelength of 572 nm. Unlike brightness, which is measured in the blue portion of the spectrum, opacity is predominately measured in the green or greenish yellow portion of the spectrum with some response throughout the entire visible spectrum. The objective is to measure opacity using a spectral response that correlates closely with human observation. FOOTNOTE Many of the geometric and spectral variables are less critical for opacity measurements than for brightness and color because opacity is a ratio measurement. For example if a sample being measured is glossy, nearly the same amount of gloss will be present in the numerator and denominator of the ratio causing most of the gloss effect to be canceled out. Similarly the effect of fluorescence on opacity is minimized by the ratio calculated that is inherent in the determination of opacity.

Brightness Basics • Brightness measures the light reflectance in the blue region of the visible light spectrum. • Optical brightening agents (OBAs) increase the reflectance of blue light. • To increase brightness measurement: • Increase OBA • Increase UV energy in light source Measuring Brightness Brightness can be measured by a variety of methods. Garmin Keygen 2016. On any given paper, the brightness number given by each of these methods will be different.

Papers may be sold based on TAPPI, ISO or D65 Brightness. Enterprise Group papers are sold based on TAPPI Brightness. Many competitive products are sold using any one of these brightness scales and it is important to understand what measurement they are using when comparing to Enterprise Group products. TAPPI Brightness - the North American standard that quantifies the brightness of paper as it would be perceived in an environment that is illuminated with a mixture of cool-white fluorescence and some filtered daylight. The ultra-violet light component of TAPPI brightness is the lowest of any standard. In addition, light hits the sample from only one particular angle (ISO and D65 brightness measurements are diffuse,meaning light hits the sample from all angles). Therefore, TAPPI Brightness will provide the lowest number of any of the three scales.

Sep 16, 2004. FEFCO Standards Committee: World standards - Comparison testing methods FEFCO / EN / ISO / TAPPI. Evaluation of scuffing- or rubbing resistance of an ink film or fibre surface on container board. See item at “Component papers of the corrugated board”.

TAPPI Brightness numbers will rarely exceed 100%. ISO Brightness - the European standard that quantifies the brightness of paper as it would be perceived in an environment that is illuminated with a mixture of cool-white fluorescence and some unfiltered daylight. The fluorescence present in a paper sample, which can provide a significant contribution to brightness, will be stimulated more using the ISO standard versus TAPPI. Therefore, the ISO standard will always yield a higher brightness versus TAPPI for the same paper. ISO Brightness numbers can exceed 100%, but not by too much.

D65 Brightness - a measurement that is based on perceived brightness for paper viewed in north sky daylight. Because outdoor light has the maximum amount of ultraviolet light available to interact with the fluorescent component of brightness, it will produce brightness numbers that are significantly elevated and could easily exceed 100%. D65 brightness numbers will always be much higher than TAPPI or ISO for the same paper because of the highly magnified fluorescence component.