2 THE USE OF THE VCR AS A METHOD OF RECORDING INFRARED IMAGES

THE TRADITIONAL METHOD of recording information from an infrared vidicon unit is to photograph with a conventional film camera directly from the television monitor. This method has the advantage of producing black-and-white prints and negatives. One disadvantage is a loss of focus around the edges of the photograph because of geometric distortion due to the curvature of the screen; a number of institutions have purchased a monitor with a flat screen to compensate for this problem. In addition, the recorded image is not immediately available.

Overall scanning, from edge to edge, of a painting has to be done frame by frame and results in the construction of a photographic mosaic. The process of making a photo-mosaic has its own problems: difficulty in matching the image at the edges of the prints, and differences in density of the prints. The difference in density is partially caused by the IR camera which automatically adjusts the image as it moves from light to dark. The result is that the mosaic, which is extremely time-consuming to construct, is difficult to read.

In using a video cassette recorder for recording infrared images, the output of the infrared camera is hooked directly into the video recorder. A painting was examined first by infrared, and decisions were made about exactly what to record. The actual process of recording went very quickly; the examination and recording of infrared images of about a dozen paintings were made within one afternoon. With experience, the whole process could go much faster.