What a Colorful World

by Louis D. Silverstein

Color displays have become a part of everyday life. From television receivers to computer monitors to automobile dashboards and even aircraft-cockpit instruments, the (once) ubiquitous color cathode-ray tube (CRT) introduced modern color technology into our lives. With the advent of the shadow-mask color CRT around 1950 and the widespread introduction of color television in the late 1950s and 1960s, color display technology achieved important status. Color television continued to evolve and with it came heightened interest in other applications for electronic color imaging. However, despite the popularity and relative maturity of color television, most information-display and graphics-imaging applications were constrained to monochromatic display devices until the middle to late 1970s. The widespread use of color displays awaited the ready availability of computers and particularly the astonishingly rapid developments in microprocessors and personal computers that began in the late 1970s and early 1980s. Obviously, computer technology provided the necessary processing power to enable color images to be generated and stored efficiently, but, perhaps more importantly, computers offered the means to effectively encode, manipulate, and control color in electronic-display systems. From this starting point for contemporary color imaging, in only a scant 25 years, we have witnessed almost exponential growth in both the technology and application of color.

In the recent past, consumers and system developers had only very limited options when selecting a color display. Few technology alternatives to the color CRT existed. Although the venerable color CRT still commands a portion of the market, this device has undergone steady declines in market share as newer, more-compact, and more-efficient display technologies have come to the forefront. Today, we are confronted with a remarkable proliferation of display technologies capable of generating full-color images. Regardless of the display technology employed, the common emphasis in virtually all application markets is on improved display image quality and lower display cost. Desired image-quality improvements for all displays consist of enhancements in contrast, luminance, and both spatial and temporal resolution. Although color displays are not required for all applications, color has become so ubiquitous that it has almost become a de facto requirement for consumers. Moreover, consumers are growing ever-more knowledgeable about color, leading to expectations for improved color performance in the form of wider display color gamuts, enhanced color saturation, and more-accurate color rendering for all applications.

Advances in display color performance have in turn provided the impetus for advances in display color science by demanding new methods to measure, describe, control, and utilize color in imaging systems. Moreover, recent advances in color imaging have even stimulated new ways to think about color and new paradigms for using color to improve visual performance and to enhance image understanding. It is against this backdrop that the Society for Information Display (SID) and Information Display magazine offer this Special Issue on Advances in Display Color Science. We have assembled a set of four leading-edge articles by prominent experts in color science to help guide our readership into the future of color information display.

Charles Poynton, a well-known consultant in digital video and color imaging, provides an overview of wide-gamut color displays. The article describes ongoing efforts to expand the color range of displays and generate robust, standardized specifications for wide-gamut imaging systems. In addition to the motivation and methods for achieving a wide color gamut, Poynton delves into the characterization of gamut coverage, color transformations and gamut mapping, wide-gamut image coding, and finally a description and discussion of the emerging xvYCC standard for wide-gamut consumer video.

An informative and insightful treatise on metamerism and its impact on multi-primary displays is offered in the article by co-authors Michael Brill of Datacolor and James Larimer of ImageMetrics. While metamerism – the matching of color stimuli with different spectra – is clearly a feature of human color vision and the basis of most methods of display color synthesis, these authors reveal the fragility of metameric color matches and how the rules of metamerism can easily be violated in displays that utilize more than three primary colors for synthesis of a wide color gamut. Brill and Larimer further describe an elegant model and solution for avoiding on-screen metamerism in multi-primary displays.

High-dynamic-range imaging is another emerging technology trend that has a major impact on how colors are rendered and perceived on displays. Rodney Heckaman and Mark Fairchild of the Munsell Color Laboratory at the Rochester Institute of Technology offer an important and thought-provoking exposé suggesting that much more is possible in achieving brighter and more-vibrant colors that may even transcend our typical experience in terms of dynamic range and an expanded perceptual gamut. Exploiting the powers of adaptation within the human visual system by, in effect, "pushing down" the white point of the display, these authors demonstrate, both empirically and with a limited set of images, a striking gamut expansion in the perceptions of lightness, chroma, brightness, and colorfulness over those achieved in traditional display configurations.

The final article of this special issue addresses the relative merits of spectral versus colorimetric imaging for color-critical display applications such as soft-proofing and medical imaging. This interesting and creative article, contributed by Dan Eliav and Moshe Ben-Chorin of Genoa Color Technologies, contrasts the methods involved in spectral color reproduction from those typically employed for colorimetric reproduction. The authors describe a prototype six-primary-color sequential rear-projection system for spectral soft-proofing in which the spectral basis functions match the normalized transmission spectra of the printing inks and their overlaps with respect to the selected paper of the print. An evaluation of the color-rendering performance for this exciting new approach revealed high reproduction accuracy, and Eliav and Ben-Chorin further describe the successful application of the prototype spectral system to the color-critical soft-proofing of advertising copy for a high-profile fashion magazine.

On behalf of the SID and as Guest Editor of this Special Issue on Advances in Display Color Science, I hope that you find the articles in this issue to be informative, interesting, and a beacon to a more colorful future.