An increasing number of libraries and archives continue to initiate digitization projects where new equipment and updated technology make it practical to digitize books and documents in color. In the past, much of the work being done with book scanners and camera-based systems captured only black and white or grayscale images primarily for their content. In the past few years, systems and cameras have evolved and the capturing of color images depicting additional context of the selected materials has become desirable and affordable. Many of the systems used for this work including overhead book scanners, commercial book cradles and specially designed holding devices used with photographic copy systems, use glass or other transparent material to hold the page or pages of a book or document flat for image capture. As there is no readily available information on the specific effects that an intermediate element in the digitization process has on the accurate color management of an image captured in this manner, this paper will provide an analysis of those effects on the color profiles created.Although there are types of glass advertised as being optically clear as compared to ordinary glass, the metal oxides in standard commercially available sheet glass of any type generally impart some tint or color (normally green) to the glass itself. Therefore, these optical properties have the possibility of adversely affecting the actual color of an image being captured when a glass platen is used to hold or flatten documents in the digitization process. This research investigates the associated effects of capturing images through transparent materials of various types in an attempt to determine how accurately the color profile generated can compensate for any color shift. Image capture was performed with both high frequency fluorescent copy lamps as well as photo strobes to determine any advantages or disadvantages to the lighting system used.A high quality digital camera optimized for copy photography was used along with standard color calibration targets to create the digital images used in the investigation. International Color Consortium (ICC) Profiles were generated and analyzed with commercially available software tools to determine the relative accuracy of their transformation and the resultant color gamut. The analysis compares the results of the images captured through glass platens of various commercially available forms to that of a control target captured without any intermediate element. Lighting uniformity and intensity were standardized for the sample sets with both systems used. All variables associated with the camera copy system and processes used to capture the images and the profiling processes were minimized to the maximum extent possible.The conclusions derived from the analysis, including the variables noted due to the use of the alternate lighting systems and how the color accuracy of the digitized images were affected, are detailed. Recommendations are made as to the suitability of the various transparent materials when they are used as platens to flatten pages of a book or document.
Paul Howell, Miranda Howard, "Effects on Color Management when using a Glass Platen to Flatten Book Pages or Documents while Capturing Images with a Digital Still Camera" in Proc. IS&T Archiving 2009, 2009, pp 219 - 223, https://doi.org/10.2352/issn.2168-3204.2009.6.1.art00048