AIC's 52nd Annual Meeting

Old photographs, thanks to their realistic way of showing the world in the past, are one of the most interesting groups of archival materials. At the same time, they are very unstable objects, sensitive to external factors, sometimes improperly produced, which has a significant negative impact on their state of preservation, the legibility of the content and the viability of the media. One of the methods of preserving photographic images for future generations, in addition to proper storage and natural for conservators to take care of preserving the original matter of historical objects, is digitization, currently understood as the production of digital copies from archival materials using cameras and scanners. This raises the question of how much a change in the imaging method could be helpful in reading damaged data, and whether the classic digitization process, especially for extremely valuable or damaged objects, should not be extended to the production of MSI files. The experiments discussed in this presentation can help assess how useful multispectral imaging is in studying and documenting archival photographic collections, and whether the imaging process should be built into the process of creating digital backups of these archival materials.

The set used for research allows the recording of monochromatic (black and white) images in 12 wavelengths, ranging from 365 to 940 nm. The silicon matrix allows to capture images in this spectral range. In addition to these 12 component images, fluorescence images are also recorded - the objects were illuminated with e.g. UV light and recorded at a wavelength of 450 nm (blue), 520 nm (green), etc. From the resulting set, 15-20 photographs, you can then create colorful images by selecting three spectral channels for the RGB channels that best visualize the information we are looking for.

The research was carried out on the photographic resource of the National Archives in Krakow. The study involved photographic materials produced using various technologies, e.g. albumen prints, collodion prints, gelatin-silver prints, as well as photographs taken using the unique magic photography technology. The examined objects include faded, chemically unstable, permanently dirty, microbiologically infected or fire-damaged photographs. Each time, mutispectral imaging made it possible to read and extract invisible content. MSI is also a helpful tool when identifying the technology of taking photographs, especially multi-layered ones, made using unique techniques, where it allows the range of technological layers, retouching or varnishes to be legible.