Spectral imaging using a commercial colour-filter array digital camera
| Hlavní autori: | , , , , |
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| Médium: | Kapitola |
| Jazyk: | angličtina slovenčina |
| ISBN: | ISBN 1-84407-253-3 |
| On-line prístup: | http://www.viks.sk/chk/14tmh_30.doc |
| Abstrakt: | SUMMARIES. A multi-year research programme is underway to develop and deliver spectral-based digital cameras for imaging cultural heritage at the National Gallery of Art, Washington DC, and the Museum of Modern Art, New York. The cameras will be used for documentation, production imaging, and conservation science. Three approaches have undergone testing: a liquid-crystal tunable filter (LCTF) coupled with a monochrome camera, a six-position filter wheel containing absorption filters coupled with a monochrome camera, and a two-position filter slider containing absorption filters coupled with a colour-filter array (CFA) colour camera. The last approach is the most practical as it uses conventional digital photography methodologies and equipment and can easily be incorporated into existing museum workflows. A virtual camera model was created that predicted camera signals from incident radiation and was used to design a pair of absorption filters. The filters were fabricated and tested using a commercial CFA digital camera. Our first experiments have been very promising: Average accuracy was under 1 CIEDE2000 and about 1.5 per cent RMS for both calibration and verification data. This level of performance was superior to our other, more complex approaches. CONCLUSIONS. A high-resolution, medium format, production colour-filter-array (CFA) digital cameraback, the Sinar 54H, was modified to facilitate spectral imaging. Modifications included replacing the IR filter with clear glass and fabricating a pair of filters that when positioned sequentially, resulted in six channels sampling the visible spectrum between about 390 and 760 nm. Transformations were derived enabling both spectral estimation and high-accuracy colourimetric imaging. The accuracy achieved equaled or exceeded much more complex imaging systems. This approach offers numerous advantages. This type of camera is very familiar to museum-imaging professionals. Thus, spectral-based imaging can be readily incorporated into the museum imaging workflow, greatly improving efficiency by eliminating visual editing. Scientific imaging can be the providence of the imaging department rather than requiring the resources of a conservation scientist with colour imaging expertise. Since only two images are captured, image registration is straightforward, often a limiting factor in achieving efficiency, for example Liang et al. (2004) and Ribés et al. (2004). If commercialized, the multi- filter CFA camera can produce both colour-managed RGB and spectral digital masters. The RGB images can be used to create derivative images for web-based display and for on-demand and catalogue printing. The spectral image can be used for conservation science, lighting design by rendering the image under various lighting conditions (Berns and Merrill 2002), and future pedantic research. In conservation, the spectral image can be used as an aid in inpainting (Berns et al. 2002, Berns and Imai 2002) and pigment identification (Liang et al. 2004), for documenting long-term colour changes (Saunders and Cupitt 1993), digital rejuvenation (Berns 2004, Berns et al. 2004a), and pigment mapping (Baronti et al. 1998), among others. |
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| ISBN: | ISBN 1-84407-253-3 |
