*2.4. Transmitted Light Imaging*

Watermarks are thinner regions of antique laid paper that when viewed in transmitted light appear lighter than the surrounding fibers. Early modern paper manufacturers placed watermarks into their papers by weaving of patterns into the wires of the screen-like molds used to shape paper sheets. Here, transmitted light images of the prints were captured in order to better visualize any watermarks within the sheets. After slipping a light sheet between each print and its mat as described in [27], one photograph was taken in ambient light and another with the print illuminated from below with the light sheet. A weighted subtraction of the two images was performed using the algorithm outlined in [28] in order to increase the visibility of watermark data within the sheets. Captures were made with a Canon EOS 50 Mark III DSLR, fitted with a Canon Zoom Lens EF 24–105 mm and with a Daylight Wafer 2 LED light table (model number D/E/U/A 35030).
