Original recording format in which material is stored — film stock, DCP, digital file. Determines durability, scalability, and archival longevity.
You hold the original in your hand — or perhaps not, because it’s long been residing on a server. The master medium is the physical or digital substrate on which your finished edited footage is first stored. Not the copy, not the working file — the original. In celluloid days, this was the 35mm negative or the DCP interpositive; today, it's usually ProRes files, DNxHD sequences, or uncompressed RAW files on redundant storage infrastructure. The master medium determines how long your film breathes before it decays or becomes obsolete.
In practice, you notice this immediately: if you store on LTO tapes, you'll need new hardware to read them in five years. Celluloid negatives require climate-controlled vaults and an inspection print every ten years. Digital files on standard HDDs? A nightmare — data corrodes, the controller dies, the industry forgets the format. That's why professional archives create three copies: an active working copy, an on-site backup, and a geographically separate backup. This isn't paranoia — it's the archival standard at Netflix or film museums. Your master medium must be migratable: it must be transferable to future formats without loss of quality or metadata integrity.
This term isn't used on set, but it becomes central in the DI and finalization stages. When the producer asks, "In what format are we delivering the masters?" you answer: "On which master medium — DCP, ProRes 422 HQ, or uncompressed?" This determines costs, delivery times, and international compatibility. A DCP is reliably preserved for ten years, but only on certified storage media. ProRes is playable everywhere but degrades slightly with each conversion. Uncompressed is archivally the safest but requires massive storage.
The critical mistake: believing that digital lasts "forever" because it doesn't get scratches. That's not true. Bit rot is real, file systems fragment, checksums raise alarms — and then you're sitting in front of a 40-year-old film that only exists on Betamax players that no one builds anymore. So, choose your master medium not for convenience, but for durability and future readability. This is craftsmanship responsibility for the film itself.