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The Light Stuff:


  • The Light Stuff:

    GTI’s Illuminating thoughts on ISO 3664.:2009 and color viewing environments

    Sean O’Leary

    As printing technology gallops like a runaway stagecoach along the digital trajectory, one critical production facet persists as decidedly analog and human: the dream of universal color viewing environments. Especially for higher value creative projects, the standardization of color evaluation supply chains is essential across the creative/production continuum. Designers, brand owners, agencies, photographers, pre-press and printers all need to eyeball images, soft proofs and prints in consistent viewing environment. This statement is all the more applicable when the workflow incorporates digital elements such as flat screens, cameras and software platforms that impose divergent color spaces along the way.

    For the past decade, the international color viewing standard for graphics and photography has been ISO 3664:.2009 an upgrade of the benchmark previously revised in 2000. In 2009, the tolerances were tightened again for D50 daylight viewing conditions, with the objective of improving quality control and ultimately minimizing miscommunication during color consultations. Tolerances for color quality were reduced by 75%, the light intensity target was changed and the neutral gray surround was "harmonized" (see below). The updated standard specifies CIE Illuminant (light source) chromaticity coordinates for D50 temperature, spectral power distribution and color rendering index.

    A key improvement in the 2009 specs was a more accurate simulation of D50 in the ultraviolet range, basically increasing the quantity of UV spectrum in the lamp and reducing allowable metamerism. Natural daylight includes a UV component which activates optical brightening agents (OBA) in printing papers, which can influence color rendering. The objective was to visually highlight the effect of OBAs so they can be color managed.

    Ten years later, ISO 3664 continues to provide guidelines that allow lighting engineers and manufacturers to design, test, and certify systems. But how do printers and graphics shops go about making sure they are sourcing a compliant viewing booth?

    You Can’t Beat The System

    According to Robert McCurdy, President of GTI Graphic Technology Inc., evaluation of a color viewing scenario begins with the light source. Based in Newburgh, NY, GTI is a major manufacturer of tight tolerance viewing booths for the graphics, photographic, and industrial color industries, with facilities in the UK and Germany. McCurdy points out that designers of professional viewing stations engineer color consistency by taking a systemic approach.

    While it is not surprising that McCurdy recommends GTI’s D50 proprietary lamps, it is hard to argue with his reasoning.

    “For generic 5000K lamps, the manufacturers’ objective is long production runs with the lowest possible cost. Unfortunately, that is not going to result in color rendering attributes appropriate for color viewing applications. For one thing, they may not emit enough ultraviolet energy to accurately simulate natural daylight. Users should make sure that lamps have a high CRI value (90 or better per the ISO standard) and an ISO 23603 CIE S 012/E, previously known as CIE Publication 51, rating of at least B/C.” When used in a GTI viewing booth, GTI’s D50 lamps provide a CRI approaching 95.

    In other words, you can source a 5000K light at Home Depot, but it will not be ISO 3664:2009 compliant. Light booth manufacturers engineer lamps as an integral part of a viewing system, which includes reflectors and diffusors in addition to the light source. A change in lamp formulation can create a color cast that compromise the job assessment.

    A professional viewing environment requires attention to several other factors, beginning with the surround of the booth interior. The color of the physical background makes a significant difference in the viewer’s perception of color. ISO 3664:2009 specifies a surround of neutral and matte surround. Munsell N8/neutral gray, a shade that occupies the midpoint between white and black, provides a neutral surround conditions that meets the ISO 3664 specification which calls for a 60% matte finish to minimize reflectance. GTI and other manufacturers also offer white and black surrounds as options.

    A less obvious parameter is light intensity, which means the measured output of the lamp across the viewed sample. Optimum color analysis is enabled when light strikes the viewing plane within a range between 1750 and 2250 lux. This intensity level allows tonal visibility of details in shadow areas but without washing out highlights. Related but not the same is evenness, or the distribution of light output levels as measured at equally distributed locations on the sample surface.

    An additional attribute is geometry, which applies to the positioning of the image with relation to the light source and observer. The standard notes that a booth should ,minimize spectral reflection (glare). Manufacturers have extensive experience configuring booths that eliminate glare, which can hide reproduction detail.

    Best Practices Optimize Performance

    ISO 3664:2009 aside, McCurdy points out additional issues that contribute to sustaining a viable light booth environment.

    “Sometimes, the demands of production schedules cause printers to forget that viewing booths need to be maintained the same as any other piece of equipment,” noted McCurdy. Specifically, we talk about cleaning, re-lamping, and measurement.”

    Regular wiping down of the light booth removes any stains or discolorations that can compromise the viewing environment. Likewise, lamp lenses should be cleaned to assure consistent output. And according to McCurdy, it is essential to periodically replace lamps in viewing booths, as performance depreciates over time.

    Remember there is a compelling economic objective behind the investment in professional viewing booths. In the context of a sophisticated workflow, efficient color communications among stakeholders reduce errors, remakes and proofing cycles, thereby increasing turn-around and profits. In this context, cutting corners defeats the purpose of the original investment.

    The Eye of the Beholder
    Finally, the ISO 3664:2009 standard references that most arcane of components: the human observer. The final piece of the compliance puzzle is an “observer with superior color vision, as rated with the FM-100 Hue Test as specified in ASTM E1499, Guide for Selection, Evaluation, and Training of Observers.”

    This is as it should be, as the final printed product will be used and viewed in an actual world, which remains human and analog – at least for the time being.

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