Robert Harris started a thread on the home theater forum talking about his involvement in the latest restoration of Spartacus.
They went back to the original (but faded) 8-perf 35mm elements and the techniques used to get the color back were interesting. According to him:
The original negatives are scanned, and the yellow dye layer is dropped, leaving the magenta and cyan, which are also both faded to varying degrees, but can be massaged into place.
To be a bit simplistic, the Y master record, which has different gamma and sizing than the Oneg is then scanned, maneuvered into position, and mated with the two extant dye layers.
There are different means of registering, but it must be… Perfect.
One further piece of information that I can offer. Spartacus is an extremely complex restoration, for which Universal pulled out all the stops.
Different shots / sequences in the film are derived from a mix of:
A. OCN + Y
B. Y + C + M
C. C + M + M (at a different gamma) to substitute for a missing Y
All of this must then be conformed to work together very seamlessly."
All of the information is really interesting, you should take a look and get ready to pick your jaws up off the floor when you see the comparaison with the older bluray:
http://screenshotcom…mparison/138930
http://screenshotcom…mparison/138929
http://screenshotcom…mparison/138932
http://screenshotcom…mparison/138933
http://screenshotcom…mparison/138934