The resolution VFX compositors actually work in during post — typically lower than final delivery specs. Saves render time, speeds up iterations and client feedback rounds.
You're sitting in the compositing room, the editor hands you a 4K DCP timeline — but you'll be working at half resolution, out of sheer necessity. The working resolution is the peace treaty between ambition and reality: it's lower than the final deliverable because tracking, roto, and compositing would otherwise become a test of patience. A 4K shot with multiple layers, keying, stabilization, and motion graphics — rendering this in true 4K takes a long time. At half or a third resolution, the preview loads in seconds, not minutes.
In practice, this means: you track an actor in 2K when the final delivery is 4K. The tracking points scale up linearly — this works as long as the markers are in place. With complex grain or very fine details, it gets tricky; you'll have to touch it up in full resolution at the end. Some shops even work in 1K for quick iterations and only switch to the actual target resolution for the final pass. This saves you real hours in revisions when the director realizes after take 47 that the glow should be different.
The workflow is standard: you generate your proxy files (usually ProRes, DNxHD, or similar) from the source material, work with them, and at the end, the network is rendered up to the final resolution — either through rerendering or intelligent upsampling techniques. Important: the working resolution must be large enough to see detail, but small enough so the system doesn't crawl. With 6K cameras, it gets critical — you need storage and GPU power that not every budget allows.
Another advantage lies in the feedback loop. With working resolution, you get a preview in ten minutes; in final resolution, it would take two hours. The client is sitting next to you, wants to see something — and with proxy resolution, you respond in real-time. This changes the entire tone of the review. Just make sure your color calibration and grading reference remain aligned with the final resolution; otherwise, you'll have surprises at the output.