This short documentary is one of several extra features on the 2004 DVD of GWTW. It contains interviews with several top technical people involved in the restoration process including Rob Humme Snr VP Production Technologies Warner Bros., Richard Edmund ASC, Janet Wilson Telecine colourist Warner Bros., Ned Price VP Mastering, Warner Bros., James Young CAS and Chris Coolson, Chief Technology Officer, Warner Bros;; they describe the process in detail in clear everyday language illustrated with some 'before' and 'after' shots without getting involved in the more abstruse aspects. Most of the documentary is devoted to the actual film restoration but the last part deals with the new stereo sound track.
Firstly the basics principle is explained of how a technicolor camera works by splitting the image into three separate colour components red, green and blue using a prism. Each of these images is recorded separately on its own black and white film. Using a dye transfer process (not explained) a composite print is made which can then be projected in the same way as a normal black and white film. Technicolor themselves went to great lengths to ensure that the dyes used in printing their films would not decay over the years so a 1939 print is today as faithful as it was in 1939. However moisture can cause the film warp so the shape of the picture is no longer perfectly rectangular.
The restoration mainly involved re-registering and realigning the three colour components in the final print. In 1939 these were inferior to present day standards. This was vividly illustrated by side by side comparison of stills from scenes shot in silhouette such as the birth of Melanie's baby. These are best viewed by freezing the DVD picture. A clear coloured outline is seen in the 1939 print as the three colours do not lie on top of each other exactly whereas the coloured halo vanishes completely in the 2004 print . By projecting a digital image the original registration error was found to be about five pixels.
Previous restorations such as the wide screen version had introduced distortions including cropping the frames to convert them to the new format. The new restoration has gone back to the original Technicolor negatives and used the original colour reference print from 1939 used at Technicolor in order to produce faithful colour replication of the prints of that time. A software technique called 'edge detection' was used to scan the film frame by frame from the centre outwards. One very informative sequence, which really needs to be viewed in freeze mode, shows the three colour negatives side by side together with the uncorrected and corrected inverse images and finally the composite print in red, green and blue. Particular attention was paid to such parameters as hue, saturation and contrast. This work was done by an outside lab which worked to the strict Warner Bros. overriding edict that nothing must be added to the 1939 film.
The final result is truly outstanding as the picture has a clarity and crispness unimaginable in 1939 and now of 21st century standard.