The options
| Method | Lossless? | Character |
|---|---|---|
| NONE | Yes | No compression. Huge files, fastest possible reads. |
| RLE | Yes | Run-length encoding - only wins on flat/graphic content. |
| ZIPS | Yes | Deflate, one scanline per block - favoured for comp interactivity (Nuke reads single lines fast). |
| ZIP | Yes | Deflate in 16-scanline blocks - the workhorse default for renders. |
| PIZ | Yes | Wavelet-based; often the best lossless ratio on noisy/grainy photographic content. |
| PXR24 | Lossy for float | Rounds 32-bit floats to 24 bits (half and int stay exact). Fine for some depth data, not for masters that specify float precision. |
| B44 / B44A | Lossy | Fixed-rate blocks built for realtime playback of half data, not for archives. |
| DWAA / DWAB | Lossy | DCT-based (JPEG-like) with a quality knob; dramatically smaller files. DWAA groups 32 scanlines, DWAB 256. |
Why delivery specs allow only some
A VFX pull or master is working material: it gets comped over, regraded, retimed and re-rendered, often through several vendors. Lossy compression bakes in error that compounds at every generation - so specs for pulls and masters almost universally require lossless (ZIP/ZIPS/PIZ, sometimes uncompressed), and reserve DWAA-class compression for review media where generational loss dies with the viewing.
Practical picks
- Rendering for delivery: whatever the spec says - and when it says "lossless", ZIP is the safe default, PIZ if your content is grain-heavy and size matters.
- Working comps: ZIPS trades a little size for faster scanline access in interactive comp work.
- Internal review sequences: DWAA/DWAB shine - just keep them out of the delivery folder.
The failure mode is not choosing wrong on purpose - it is one machine in the farm carrying an old preset. The header of every EXR records its compression, which is why a header-level batch check catches this in seconds. Shot Delivery Preflight reads the first 64 KB of sampled frames and flags anything outside the spec's allow-list.