Kodak's 10-bit log image format — captures film scans with massive dynamic range. DI and color grading standard for decades, largely superseded by DPX now.
Kodak developed Cineon in the early 90s in response to a fundamental problem: how to store a complete film print digitally without losing the fine gradations of grayscale and dynamic range. The result was a 10-bit log format that radically differed from classic linear RGB. Logarithmic encoding resembles the characteristic of film emulsion – more bits for the shadows, where the eye is sensitive, and fewer in the bright areas. This allowed for the actual scanning of a 35mm negative with all its details packed into a file.
In practice, this meant that with Cineon files, you had extreme latitude for color grading. If the scan turned out dark or the exposure on set wasn't optimal – no problem. The log curve stored so much information that even aggressive grading operations left no banding artifacts. Therefore, Cineon became the standard output format for Digital Intermediate workflows from the mid-90s onwards. Every studio that professionally did DI worked with Cineon sequences. You scanned your film into Cineon, fed it into the grading system, and at the end, you outputted back to 35mm.
Technically, however, Cineon was storage-intensive – huge frame sequences, hardly any compression. And the format itself was proprietary, not ideal for archiving. Therefore, DPX soon established itself as its successor – essentially the same principle (10-bit log, linear image sequences), but more openly documented and developed into an SMPTE standard. Today, you hardly find Cineon in modern workflows. DPX took over, later Grundig in the HDR context, and proprietary formats like ProRes 422 HQ for faster pipelines.
Historically, however, Cineon remains important: it was the first format standard that truly brought film and digital to the same level. Without Cineon, DI would not have gained the credibility it needed in the early 2000s. If you still encounter Cineon sequences in older projects today, you know – that's true archival quality. Treat the files accordingly.