Several digital film restoration techniques have emerged during the last decade and became more and more automated but restoration evaluation still remains a rarely tackled issue. In the sphere of cinema, the image quality is judged visually. In fact, experts and technicians judge and determine the quality of the film images during the calibration (post production) process. As a consequence, the quality of a movie is also estimated subjectively by experts in the field of digital film restoration. On the other hand, objective quality metrics do not necessarily correlate well with perceived quality. Plus, some measures assume that there exists a reference in the form of an "original" to compare to, which prevents their usage in digital restoration field, where often there is no reference to compare to. That is why subjective evaluation is the most used and most efficient approach up to now. But subjective assessment is expensive, time consuming and does not respond, hence, to the economic requirements. After presenting the several defects than can affect cinematographic material, and the film digital restoration field, we present in this paper the issues of image quality evaluation in the field of digital film restoration and suggest some reference free objective measures.
Digital film restoration is a significant hope for cinematographic archivists. Technical progress, more powerful machines at lower cost, makes it possible nowadays to restore cinematographic archives digitally at acceptable paces. Several digital restoration techniques have emerged during the last decade and became more and more automated but restoration evaluation remains still a rarely tackled issue. After presenting the several defects than can affect cinematographic material, and the film digital restoration field, we present in this paper the issues of image quality evaluation in the field of digital film restoration and suggest some reference free objective measures.
With the collaboration of Thomson Broadcast Ex Machina has developed a full digital tape-to-film transfer process. This system accepts as input any European Analog or Digital formats: 1 inch B. T. S. 4xDl. . . It is based on a fully computerized image processing and is fully automated from the loading of the Dl tapes to the 35mm negative output. This process includes spatial and temporal filtering to get full scan 35 mmimage quality. As the input format is 50 fields per second (non-square pixels) and the output format is 24 frames per second (square pixels) the key point was to obtain a good spatial resolution without dynamic artefacts like excessive blur moving images or patterns at vertical edges. Steps of the process are as follows: - Digital copy on four 4:2:2 tapes as necessary - Transfer on computer network - Adaptive filtering by software - Gamma correction and output on 35mmfilm recorder. The processing speed has been improved by controlling four processes in parallel. High Definition tape to film transfer is available right now. The transfer capacity is 30 minutes per week since the end of last year. 1 - PRESENTATION OF THE PROJECT With the collaboration of THOMSON Broadcast Ex Machina has developed a fully digital High Definition tape-to-film transfer process. This sytem is designed to permit transfer on 35mm film of productions made with the European High Definition Standard. As a computer graphics production company Ex Machina has been producing sequences on various media including digital video high definition video 35 mm film and has finished recently a 3 mn film on 70 mm IMAX format. Two ongoing projects use this same standard with one having been designed for stereoscopic projection. Building on this expertise Ex Machina proposed to realize a tape to film transfer system for the European Economic Interest Grouping (EIIG) Vision 1250 in co-operation with another european organisation Eureka 95. For the development of such a system the company proposed to use commercialy available equipment with no custom hardware and to write the software needed for mastering the whole process. This approach offers numerous advantages: - it is fast in terms of both development and operational build-up - it is flexible as both software and equipment may evolve - itis less costly considering the time and effort needed. 124 I SPIE Vol. 1656 High-Resolution Sensors and Hybrid Systems (1992) 0-8194-081 0-71921$4. 00