Digitization at UNC-Chapel Hill
At UNC-Chapel Hill, maps are digitized in the Digital Production Center in the Carolina Digital Library and Archives. Maps up to 11" x 17" are digitized on a flatbed scanner, while larger maps are digitized using the vacuum frame and camera back described here.
Maps are imaged by placing them within a 4’x 5’ Teaneck Vacuum Frame (an industrial graphic arts tool). This frame sandwiches the map between glass and the back of the frame. Once switched on, the vacuum removes the air, ensuring the map is completely flat during image capture.
The vacuum frame is illuminated by four, 600-watt North Light HID (High Intensity Discharge) Copy Lights.
Maps are scanned using a hybrid imaging system. A BetterLight Large Format Digital Scanning Camera Back, Model Super 8K-HS, is used with a Horseman 450XL 4”x5” studio camera and a Rodenstock APO-Sironar Digital 180mm f/5.6 lens. The system is mounted on a Cambo UST studio stand. The distance between the stand and the vacuum frame is adjusted depending on the size of the map.
Maps are captured at 100% of their original size, 300pixels per inch using the TIFF file format. File sizes typically range in the hundreds of megabytes.
Scan times are usually between 3.5 and 7 minutes.
All post-capture work is done on a Mac Pro with dual Intel processors using Adobe PhotoShop CS3.