I'm sure Mr Harris will have some things to say on his own, but he has already expressed in interviews that some restoration projects just aren't feasible using photochemical means alone. For example here is a comment he made regarding the restoration of The Godfather Parts I and II.
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In consultation with Rick Utley, Pro-Tek’s vice president of preservation services, Harris determined that a photochemical restoration was out of the question. “Not only that,” he says, “but we determined that the original negative of The Godfather should never be run through a pin-registered mechanism. It could crack up.”
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The project stayed at 4K throughout the restoration, and Harris says this capability was key to the team’s success. “Paramount didn’t wait to do this work because they didn’t want to invest in it,” he says. “What was necessary was the ability to work in true 4K resolution; anything they might have tried on the digital side before that would have been a waste of time.” Often, the DI process is carried out with 2K proxies, but some adjustments, including noise reduction and sharpening, do not translate well from one resolution to another. In this case, occasional sharpening and noise reduction were necessary, largely to even out differences among the many elements Harris brought in to remedy problems. He explains, “We started scanning bits and pieces of separation masters, interpositive, CRI [Color Reversal Intermediate], internegative — anything from which we thought we could harvest what we thought was the finest image. One would be sharp but wouldn’t have the right color; another had the right color but was soft or damaged.”
http://www.theasc.com/magazine_dynamic/May2008/PostFocus/page1.php
Digital restoration isn't increasingly popular simply because it makes better looking Blu-rays. It is a powerful tool because it enables a lot of restoration techniques that just can't be achieved photochemically. Compare the Blu-ray of The Robe to the original DVD edition to see what can be done with modern restoration tools. Warner Bros. has reissued North By Northwest in new 35mm prints made from the recent restoration that will also be used as the master for the Blu-ray. At this year's Cannes festival The Red Shoes was shown on a new print made from a restoration of the 3-strip Technicolor elements. 4K and now even 8K resolution is good enough to scan the negatives, make a new restoration negative that can be used to make prints.
Edited by Simon Howson - 9/14/09 at 6:43am