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1. DIGITAL MIRACLES
- Baylor University Press
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1 CHAPTER ONE DIGITAL MIRACLES: REVEALING INVISIBLE SCRIPTS Keith T. Knox, Roger L. Easton, Jr., Robert H. Johnston INTRODUCTION Since their discovery in 1947, the Dead Sea Scrolls have been recorded and studied using photographic imaging techniques. Although much has been learned from the study of these photographs in the last five decades, there is a limit to what a magnifying glass can reveal. In the commercial world, great strides have been made in the last ten years in the capture, storage, and processing of digital images. These digital imaging technologies have matured to the point where they are now readily available at a reasonable cost. Scholars have only recently started applying these techniques to the task of uncovering and deciphering degraded writings. We have been fortunate to have been involved in this exciting integration of imaging science and the study of ancient documents. In our studies, we have explored several methods for revealing characters in degraded texts. Some involve illuminating the document with light that is invisible to humans; others involve computer processing of the image to reveal or enhance text characters. The choice of method (or combination of methods) depends upon the particular artifact or document being studied. In cases where the inks have faded, images obtained under illumination from ultraviolet light may reveal characters that are either difficult to distinguish or totally unreadable when viewed by eye. If the parchment has darkened due to the effects of age or exposure, illumination with infrared light may reveal otherwise unreadable characters. Both of these techniques require that the original scrolls be available to be imaged, and the images may be further enhanced using digital imaging techniques. Even if scrolls are not available for direct examination , photographs may be processed in a digital computer to enhance subtle color differences between ink and parchment and may reveal new characters. In the work reported here on the Dead Sea Scrolls, we have 2 DIGITAL MIRACLES used images of actual documents obtained under infrared illumination and color digital image processing of photographs taken by others. In both cases, additional characters have been revealed. THE ROLE OF ILLUMINATION IN IMAGING Images are representations of objects or scenes that are created by measuring the amount of light that was reflected from objects in the scene. Before discussing the form of the images, it is useful to first describe the physical model of light itself. Light is a wave of the combined electromagnetic field. A wave is described by two primary characteristics: its maximum “height,” which is called the amplitude, and the distance between adjacent maxima, which is the wavelength. For light, the amplitude describes the “brightness” or “intensity” of the light, and the wavelength determines the color. The perceived color at each location in the scene is determined by the distribution of intensity of the light that reaches the detector over all wavelengths. The shortest visible wavelength is perceived as blue; as the wavelength increases, the color progresses through green to orange to red, which is the longest visible wavelength. The range of visible colors ordered by wavelength is the familiar spectrum seen in the rainbow. Colors perceived by the eye are based on the different responses induced by light in receptors in the retina. There are three types of color-sensitive receptors known as “cones” that are sensitive to different ranges of visible wavelengths. This fact makes it possible to display images in three appropriate colors that will be perceived in “full color” by the eye. This “trichromatic” response of the eye is exploited by all common color imaging systems such as television, which transmits images in the three additive primary colors (red, green, and blue) to the receiver. The red, green, and blue images are recombined to create an image perceived as identical to the original scene. “Black-and-white” (often called “monochrome”) images are created by measuring or displaying the reflected light over the entire range of visible wavelengths simultaneously. IMAGING OF DOCUMENTS When reading text, the “contrast” between characters and parchment is the most critical determinant of the clarity of the document. The contrast [3.144.116.159] Project MUSE (2024-04-17 21:57 GMT) KNOX, EASTON, AND JOHNSTON 3 is determined by the relative reflectances of the ink characters and parchment. Materials used as inks absorb most wavelengths of visible incident light (and thus reflect little light); this is why ink appears “black.” On the other hand, parchment in good condition reflects all wavelengths of visible light well, and...