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When a film stock is transferred into 4K, the film stock can be kept safe and used for a future transfer that would be in 8K, for example. It depends on whether the transfer was done with the original print or the newer print. With original prints, they're more likely to have been exposed to damage, due to the fact that film stock cannot last forever. 4K transfer can look better than the original film stock, since they iron out all of the problems, including gate weaving, film scratches, chromatic aberration, dust, and so forth. Some 4K transfers are done with newer stock, as is the case with 2001: A Space Odyssey, due to the original stock fading to salmon pink. It all links to preservation and the transferring that's taken place.
