MULTIMODALITY IMAGING OF DAGUERREOTYPES AND DEVELOPMENT OF A REGISTRATION PROGRAM FOR IMAGE EVALUATION
Patrick Ravines, Karl G. Baum, Nicholas A. Cox, Shawn Welch, María Helguera · Journal of the American Institute for Conservation · 2014
This study documented 260 of the whole-plate daguerreotypes of Southworth and Hawes at George Eastman House International Museum of Photography and Film using several imaging techniques in order to generate a baseline or benchmark of condition. Various existing imaging modalities—such as high-resolution scans using modified flat-bed scanners, full-frame digital cameras with special lighting arrangements for high dynamic range (HDR), long-wave ultra violet radiation (UVA) induced fluorescence, and axial specular imaging—were refined to capture the fine surface features of daguerreotypes. The methodology used here can guide other conservators interested in documenting daguerreotypes. The accumulation of a wide range of visual information of daguerreotypes from the various imaging modalities led to the development of an open source image registration (alignment) program for multimodality image comparison. The affine transform registration algorithm is based on user-defined point pairs between two images that are used to describe the displacements between them. After correcting for image shearing, rotation, scaling, and translation, the images can be directly compared allowing additional observations.