Summary¶
Lossy (final) exports¶
Especially for final exports, you probably don’t need lossless compression, and with the right settings, the exported file size can be quite small with just a very small reduction of quality, and the Master or backup of your movie can be stored this way.
In this case, DWA (with a small compression level) is very efficient in all cases. Be careful, DWA is not supported by ffmpeg (yet). In this case PXR24 is a good (lossless) alternative.
Solid colors (e.g. alpha channels) can be compressed very efficiently using RLE without losing quality.
If you’re not exporting for complex compositing (e.g. choma keying), and especially from a video source or if the export is to be used as a Master for further YUV 422 or 421 video exports (like h.264/h.265), the Luminance/Chroma option will divide the file size by two with only a very small reduction of quality. Be careful, ffmpeg does not support the Luminance/chroma option (yet).
Lossless (intermediary) exports¶
If the file is to be used in a compositing software for example, you may want to export without losing quality.
In any case, if your rendering an image with AOV (most likely from a 3D software), and you can accept a (very small) quality loss, DWA is the best option, as it will compress only the RGB channels (or Y, RY, BY in case of Luminance/Chroma) and use RLE for alpha and ZIP for any other channel. In this case, be careful that DWA uses the channel names (case sensitive):
- Lossy channels: R, G, B, Y, RY, BY
- RLE: A
- ZIP: any other name (Red, red, r, Green, green, g, Blue, blue, b, x, y, z, U, u, V, v, etc…)
Warning
Be careful with the names of the channel. For example using XYZ will result in the Y channel being lossy. You can use xyz instead.
When the images don’t have grain:
- If you don’t need full 32-bit float precision, PXR24 is the best compression you can use.
- If you need full 32-bit float precision, ZIP is the best option.
When the images have grain, PIZ is always the best option.
For stereo images, the best is ZIP.
For solid colors such as alpha channels, it’s better to use RLE.
Special cases¶
There are more specific uses for OpenEXR:
- On systems for real-time playback, B44 is preferred (or B44A for alpha channels and solid colors).
- If you need to render small-size lossy proxies, you can use DWAA with a high compression level.
- Gray-scale images will benefit a lot from the Luminance/Chroma option, without losing quality.