Documentary about the restoration of the film "The Wizard of Oz". The original Technicolor negatives were scanned at about the double HDTV-resoloution to record all the details that can be seen at full-HD resoloution (Nyquist-Shannon theorem).
The great thing about Technicolor is that each elementary color has it's own negative. Ordinary color film (negative or direct positive) has three layers. One for each elementary color. The three negative sources allow to reconstruct damaged frames from the other intact frames. This way the original negatives only needed to be scanned rather than cleaned. Every single frame of the movie was inspected by a skilled operator and retouched if necessary.
