− Noboru Koshizuka, Ken'ichi Sawada, Ken Sakamura −
Ph.1 Image before digital film restoration
From "Tokyo Story (1953, (C) Shochuku Corporation)"
Ph.2 Image after digital film restoration
From "Tokyo Story (1953, (C) Shochuku Corporation)"
Introduction
Movie is the oldest motion picture system with the highest image quality among existing motion picture systems. So, there are many valuable cultural and scientific resources recorded as movies. Tokyo University Digital Museum incorporates with digital preservation and digital restoration of old movies.
Movie and photograph are based on technology to record images by chemical transformation of materials on a film. In this technology, physical degradation of films directly degrades recorded information quality. It is passing about a hundred years since the birth of movies. The film degradation has already lost huge amount of movie art properties.
According to the survey of the Library of Congress of the United States, about eighty percents of silent movies produced in the Unites States have already been lost or in unrestorable states. Another reports that about ninety percents of silent movies produced before 1930 and about fifty percents before 1950 have been lost.
Today, digital recording is the best way to inherit the current state of a film as it is. In addition to this, digitizing a movie allow us to apply the movie the digital restoration technology, which can bring back the original images in the films from the past.
Preservation and Restoration of Movies
Movie communities, who worried about the situation in which a large amount of movie properties have been lost and are now loosing, have established several institutes in many countries. On the other hand, there are activities of digital film restoration in which movies are restored by using image processing technologies. The most famous example is a digital restoration of a popular Disney movie "Snow White" (1937) in 1993 by "Cinesite", which is the digital image center of Eastman Kodak Corporation opened in 1992. We have also been attempting digital restoration of old movies directed by "Yasujiro Ozu" since 1998.
Digital Restoration in the TOKYO UNIVERSITY DIGITAL OZU Project
We, TOKYO UNIVERSITY DIGITAL MUSEUM, are carrying out a project called DIGITAL OZU Project, in which we are trying to restore a famous movie "Tokyo Story" directed by Yasujiro Ozu. "Tokyo Story" is famous in the world as one of his best works. Unfortunately, its original negative film was lost by fire of the development office. The playing films in movie theaters and video products of today were bad copies replicated from an intermediate negative film.
In DIGITAL OZU Project, important points for restoration are as follows.
- Removing cracks, flaws, and blots
- Correction of contrast and color
- Correction of brightness
- Regulation of size and position
- Correction of sound, removing noise
In the following, we shortly present the basic process of digital film restoration.
1) Film scanning
The first process is to digitize image information recorded on films by using a special scanner for movie films. By using the film scanner, we can digitize one frame of films into about 6000x4000 dot data in 30 seconds.
2) Pre-processing
The second process is pre-processing in advance of the main restoration process. This process includes correction of errors in scanning, removing information unnecessary for restoration, film segmentation based on scene analysis, and so on.
3) Digital Restoration
The next process is the main process, digital restoration. This process firstly detects flaws and cracks on the basis of image frequency analysis, motion analysis of pictures, and so on. Image portions of the cracks and flaws are complemented by computation. Additionally, by comparing with reference films, it corrects color, brightness, contrast, and so on.
4) Making playing media
Lastly, to play the movie, all restored images are printed on movie films by using film recorder, or high-resolution digital video data.
Image restoration techniques have been used in many applications such as correcting pictures taken by artificial satellites and restoring old photo pictures. These techniques handle static pictures and restore an image independently. In case of movies, there are a large number of images. Current standard motion picture films include twenty-four frames in one second. In our film restoration, we can utilize similar images recorded in adjacent frames. As the flaw positions of different frames must be completely different, the flaw pixels can be complemented not only by neighboring pixel values of the frame but also by the pixel values of the previous and next frames. This is the most remarkable point in the movie film restoration technique.
