Chapter 7. Final Thoughts

Decades of experience in still photography, motion picture film, and broadcast video show that a good reproduction of a natural scene is not one-to-one. The optimum transfer function is non-linear. For several reasons though, it is advantageous to record a scene linearly. That is where video and motion picture film follow different paths. In video, where live broadcasting is an important application, the final image is recorded right away. Further processing is done only by the physical characteristics of the CRT monitor. When the video system was established it had not been possible to implement extensive post processing with a 3D LUT or by other means. Cinematography uses negative film, which records log scene luminance linearly and in a wider range than finally displayed. The negative is an intermediary image, it needs to be printed. Its tonal inversion is the obvious reason for this, while the separation in linear recording and non-linear reproduction is the not so obvious reason.

The DI process should maintain the two stages of the photographic system, where the recorded data is linear to the scene and non-linearly displayed. In the future, many films will be projected digitally. While it will be no longer necessary to exactly reproduce the look of print film then, the general characteristics of projection remain the same. Digital cameras may replace negative film, but a high end system will always capture the scene linearly. In professional still photography, for example, there is a strong request for “raw” camera files, which are linear files in a higher bit depth. The data may be “lin-linear” rather than log-linear, but this changes only the display LUT (even color correction in the style of printer-lights can be applied; the offsets to log data become factors to linear data).

For now, the hybrid approach - shooting on film and digital post production - seems to be best approach. The low gamma, high dynamic range, and straight-line characteristics of negative films make them well-suited for digital scanning.

Ansel Adams phrased the well-known words, “the negative is the score and the print is the performance”. But cinematographers never had the possibilities even a traditional darkroom gives to still photographers. DI puts the cinematographer into the position of a conductor, it is his or her orchestra.