5.3 FILM SCANNING 151 Extracting a medium dynamic range radiance map from a single negative is relatively straightforward since it does not require alignment of multiple frames and does not suffer from object displacement that may occur during the capture of several exposures. It therefore serves as the basis for the techniques presented later in this chapter. 5.3 FILM SCANNING In the ideal case for creating an HDR image from multiple low dynamic range (LDR) exposures, the scene or image should be completely static (e.g., an exposed and developed negative). We assume that the response curve of the film is known. In addition, the LDR capture device, such as an 8-bit/primary film scanner with known response curves, should provide some means to control the exposure exactly during multiple captures. Creating an HDR image under these conditions starts by taking scans with mul- tiple exposures. In addition, the system response is inverted to get back to a linear relation between scene radiances and pixel values. Each scanned image is multi-