Two formats, two jobs
The choice is not about quality preference - it is about what the file is for. An image sequence is finishing material: it gets ingested, comped over, graded and re-rendered, so it has to be frame-accurate and losslessly encoded. A QuickTime is review material: a single self-contained file a producer or supervisor scrubs to approve the work, where playback convenience beats per-frame surgery.
| Image sequence (EXR / DPX) | QuickTime (ProRes) | |
|---|---|---|
| Purpose | Finishing / interchange master | Review, reference, approval |
| Per-frame access | Yes - one file per frame | No - one movie, scrub only |
| Colour | Scene-linear / log, wide gamut, 16-bit+ float | Display-referred, 10/12-bit, baked view transform |
| Encoding | Lossless (ZIP/PIZ) or 10-bit log | ProRes - visually lossless but not for re-rendering chains |
| Typical failure | Missing frame, wrong compression, wrong bit depth | Wrong ProRes flavour, wrong fps, wrong resolution |
When to deliver a sequence
Deliver EXR or DPX image sequences whenever the recipient needs to do more work to the pixels - conform, comp, grade, retime, re-render. Because each frame is its own file, a sequence supports the full latitude a downstream facility needs (see ACES EXR delivery and DPX log vs linear). The trade-off is fragility: a single dropped frame, a padding change mid-sequence, or one machine on the farm writing a stray compression setting can bounce the whole package. That is exactly why sequence checks focus on contiguous frames, consistent header attributes and correct naming.
When to deliver a QuickTime
Deliver a ProRes QuickTime when the file is for viewing and sign-off, not re-rendering. One file plays anywhere, carries its own audio and timecode, and doesn't strew hundreds of frames across a folder. The catch is that "ProRes" is not one thing - it is six flavours, and the wrong one is a bounce in both directions.
The six ProRes flavours
- 422 Proxy (apco) and 422 LT (apcs) - light edit/offline media, never a finishing deliverable.
- 422 (apcn) and 422 HQ (apch) - general and high-quality review; 422 HQ is the common review deliverable.
- 4444 (ap4h) and 4444 XQ (ap4x) - full 4:4:4 chroma with alpha, for VFX review that needs a matte or the highest fidelity.
A Proxy left in from a stale export preset failing a 4444 slot, or a 4444 XQ quadrupling upload time where 422 HQ was asked for - both are routine. The full ProRes breakdown covers alpha and bitrates; the short version is: match the flavour on the sheet exactly. Frame rate matters just as much - 23.976 and 24 are different deliverables to any ingest, however identical they look in a player.
Where MXF fits (detected, not parsed)
Some broadcast and finishing pipelines deliver MXF rather than QuickTime. MXF is a flexible wrapper - its internal essence and metadata layout varies far more than a QuickTime atom tree, so it can't be reliably read header-only in the browser. Rather than guess, Shot Delivery Preflight detects an MXF and flags it for a manual look instead of pretending to validate its contents. Deeper MXF parsing is on the roadmap; for now, an MXF in the folder is called out, not silently passed.