Adopting ISO Standards for Museum Imaging Scott Geffert, imagingetc.com, Inc. (originally published 1/2008) Introduction: This document is an effort to take a critical look at the growing desire within the museum community to utilize open, international standards for the digitization and output of original two and three-dimensional objects. Over the years, there has been much discussion regarding the long-term viability of digital assets. Unfortunately, most of these discussions have been focussed on file formats and the life of storage media. While these are critical issues, there is a third and possibly more immediate concern; the current lack of standardization of the process for capture and output. While most people assume that simply implementing an ICC color-managed workflow is adequate for museum imaging, there are both legacy issues and recent advancements that users should be aware of. For those charged with both communicating about and preserving works of art it is incredibly important that digital images are carefully defined and objective standard procedures are adhered to. You may ask: “What standards?”. It is for this reason that we set out to explore the current and emerging standards that form the basis of today’s imaging practices. While the limitations of traditional film and processing made it almost impossible to achieve consistency, there is absolutely no reason why today’s digital imaging tools cannot be run in such a way as to deliver consistent, accurate representations of artworks. As electronic image distribution has made images and information more accessible than ever, it is essential that the images and information released to the public are carefully created and vetted. To illustrate the seriousness of this issue, perform a Google image search of any well- known artwork. The results will certainly be chaotic. This exercise demonstrates why standards are critical if we are to achieve consistent, trustworthy images worldwide. ©2008 Scott Geffert www.imagingetc.com Page 1 This document is an effort to begin a dialog between the imaging community, the computer industry, camera manufacturers and software developers. Our goal is to encourage everyone involved to critically evaluate the current best practices, and to explore ways we can improve the experience for users worldwide by moving quickly towards emerging OPEN IMAGING STANDARDS and best practices. While the content is technical in nature, I have tried to incorporate as many practical examples and real world scenarios to illustrate the most important issues. I have also boldfaced statements that are important to discuss further. The document has been organized around the following outline: History: A look back at the early days of digital imaging to help underscore the fact that digital imaging is a relatively new technology still experiencing growing pains. Color Management- the early years: ICC (International Color Consortium) color workflow has provided the basis for controlling the digital imaging process. This section looks back at how color management crossed paths with digital imaging. The LAB color model and how it relates to photographic exposure: Illustrations regarding the historically close relationship between the LAB color model, human vision and photography. Here you will begin to see where the existing imaging standards are illogical and where the emerging ISO (International Organization for Standardization) standards are so important as we strive to refine the process. 2007 and beyond: standards evolve and imaging matures: A discussion regarding a move towards ISO standards, the L* gamma function for working spaces and universal display calibration standards. A proposed enhancement for ISO consideration: The ISO imaging standard does not currently incorporate a wide gamut L* color space. This section discusses the possible benefits of considering a wide gamut addendum to the proposed standards. Evaluation and testing of RGB working spaces for ISO standard printing: A detailed summary of recent capture to print testing for The Rijksmuseum, Amsterdam, using new digital photography of artworks from collections around the world. This first- ever test of this scope compares the effect of the RGB working space from calibrated capture to the printing press. Conclusions and Recommendations: Discussions regarding the testing and how the community can get involved. Addendum 1 - 4 Acknowledgments: Special thanks to all of the people that made this research possible. ©2008 Scott Geffert www.imagingetc.com Page 2 History: It is important to understand that digital imaging is a relatively new technology and is only a part of a larger trend towards overall digital convergence. As new technologies hit different industries at different times, there is a ripple effect that occurs as people adapt to sometimes dramatic changes in tools and best practices. Unfortunately, during these technological upheavals it is very easy for technology to run ahead of itself to a point of diminishing returns. As digital camera, computer and software developers compete for the more lucrative consumer marketplace we are beginning to see an alarming trend away from objective tools and standardization. In order to gain a proper perspective on the scope of this problem it is important to take a look back at how digital imaging gained popularity in the late 1980’s. While CCD imagers became available for flatbed scanners and video cameras, the personal computer revolution was well underway. It was just a matter of time before these various technologies would cross paths. At the time of this convergence the most powerful desktop computers were unable to display more than 256 shades of color. The predominant computer platforms of the time were computers running the Microsoft® Windows™ and Apple® Macintosh™ operating systems. As computer manufacturers looked to display more tones on CRT displays, standards were adopted from the television industry. The Windows™ platform adopted a display gamma function of 2.2, prevalent for televisions at the time, which was well suited to making bar charts look rich and saturated on small color gamut CRT displays. Apple®, on the other hand adopted a display gamma function of 1.8 in an attempt to drive the display closer to the gamma of printed material. This decision is probably why Apple® Macintosh™ computers became so prevalent in print production. In some ways this became an early, yet passive form of color management; if you used a Macintosh™ computer, by default you were working in the color space of the Sony® Trinitron™ display (Apple RGB- 6500k white point, 1.8 gamma). At this stage of development, around 1988, digital imaging, outside of the military and high-end turnkey prepress systems, was a curiosity for most people. With the introduction of Adobe® Photoshop™ v1.0 in 1991, digital imaging became a reality. When Adobe® Photoshop™ was created it simply deferred to the computer display parameters as a basis for the dynamics of the file. Essentially, if your display was dark, you would lighten the file tonal value numbers to compensate. If your display was too blue, you would adjust the color balance to add yellow to the file to compensate. As digital printers became available, people would adjust the settings in the printer software to manually compensate for color and density shifts of the output. With careful attention, users could achieve a very high quality and predictable result in this “closed loop” color workflow. ©2008 Scott Geffert www.imagingetc.com Page 3 Color Management- the early years: The problem with a closed loop color workflow is that if you took a file out of one system and into another the process would break down completely as the closed loop would be broken. To address this problem, Adobe® and others began to ship utilities such as Adobe® Gamma. This software tool allowed you to visually calibrate your computer display to attempt to normalize the viewing environment. While this was a step in the right direction; users utilized this tool to visually match print output to create a 1:1 relationship in the workflow, ultimately, this approach did little to solve the problem of sharing files. Up until this point in time, Apple® had dominated the imaging market due to it’s closed design, but Apple®, through a series of missteps, began to falter. The Adobe Gamma™ Utility In order to help open up the Windows™ platform to imaging, Adobe® needed to come up with a method for managing the very undefined nature of the Windows™computing platform, where manufacturers and users would literally cobble systems together from any and all types of displays and display cards. In 1998 Adobe® adopted the ICC (International Color Consortium) color managed workflow method. Apple Computer®, Adobe®, Agfa®, Eastman Kodak®, Linotype-Hell®, and others created a cross platform standard for device profiling in 1993. This group became known as ICC (International Color Consortium). Devices such as scanners, digital cameras, monitors and output devices could be characterized with the creation of ICC profiles. These small files, containing numeric data which describe the characteristics of these devices could be used throughout a Color Management System (CMS), which is based on characterizing each device in the workflow and editing in a device independent “RGB Working Color Space”. ICC profiles describe the color characteristics of a particular device, defining a mapping between the source or target color space and a profile connection space (PCS). This PCS is generally LAB Color Space (defined in the next section). Conceptually, this model makes perfect sense, as it liberates the file from the platform, but it was not without flaws as implemented in 1998. It is around this time frame that museums and libraries around the world began adopting digital photography in significant numbers. After almost a decade of digital imaging, museums and other cultural institutions have still done a poor job of adopting universal standards. The ICC workflow method was adopted by the ISO standards organization in December 2005 as ISO 15076-1:2005.