Special imaging demonstration at the Croatian Conservation Institute

On 22 May, organised by the Croatian Conservation Institute (HRZ), a demonstration combined with a lecture titled “Multispectral capture of cultural heritage” took place in the ceremonial hall of the Museum Documentation Centre (MDC), Zagreb, where our digitisation specialist and Phase One expert, Dániel Bedő, presented the most specialised imaging in cultural heritage digitisation.

The event was attended by the Croatian Conservation Institute, the Croatian State Archives, the Ministry of Culture and Media of the Republic of Croatia, the Strossmayer Gallery of Old Masters (HAZU), the Museum Documentation Centre and the University of Zagreb Faculty of Graphic Arts. During the demonstration we examined canvases and archival documents in both the visible and the invisible spectrum.

The multispectral technology demonstrated on site: Phase One Rainbow

The “Phase One Rainbow” process makes it possible to use several multispectral imaging technologies in a single camera system. The point is that, by using light sources emitting in different light ranges and suitable filters, information invisible to the human eye can be displayed on digital images. For example, using the device at a crime scene, traces of bodily fluids, fingerprints or the use of firearms can be detected. The technology can also be used for many other purposes, for analysis or authentication in the fields of art history and criminal investigation. Using the device makes it possible to make poorly preserved texts legible, and to analyse polychrome surfaces (paintings, stone, other materials) or any other textile (for example, in historical research, to determine the material and age).

During imaging, the filter discs that are part of the camera system and the various light sources switch on and off automatically, controlled by the equipment’s own software, called Rainbow MSI. In this process, which takes a few minutes, 8 images are taken. The system can automatically adjust focus as a function of wavelength, so imaging proceeds without interruption. With multispectral technology we examine the analysed object by a non-invasive, that is, intervention-free, method. The 8 images must be taken every time, because the human eye cannot decide in which light spectrum the information relevant to the research or authentication process can be found.

Using light sources of different wavelengths and special filters, we recorded the artworks with the following techniques:

• IRR (near infrared reflectography)
• IRRFC (near infrared reflectography false color)
• UVIL (ultraviolet induced infrared luminescence)
• UVL (ultraviolet induced visible luminescence)
• UVR (ultraviolet reflectography)
• UVRFC (ultraviolet reflectography false color)
• VIL (visible-induced infrared luminescence)
• VIS (visible reflected)