Linear EXR workflows and recommended DWA compression
Avoiding common errors through compression
Very large file sizes can reduce speeds and increase costs. This is especially true when working with high resolutions, high numbers of render passes, high bit-rate output formats or multiple outputs. To increase processing speed, reduce download times, and even increase responsiveness in composition tools, the Render Network team recommends to work with the lossy compressed file format EXR DWAA or DWAB when using the network.
The standard was contributed by DreamWorks Animation. The reduction in size is up to 10x and the file size of a 32-Bit EXR image is roughly the same as a 8-Bit PNG which results in much better dynamic range for the end result. Tools like Adobe After Effects are also reported to be more responsive in recent versions when working with compressed files.
DWA in OpenEXR is actually two compression options, DWAA and DWAB. They use the same algorithm, but DWAA compresses pixels in blocks of 32 scanlines, while DWAB does 256 scanlines. Bundling more lines together lets DWAB compress more efficiently and increases performance when the entire entire image is read at once, as most programs do. Meanwhile, DWAA's smaller bundles make it more efficient for reading just a few scanlines at a time, as Nuke usually does." For the full breakdown, click here
For more information on EXR Data Compression types please read this article
The following are two videos which are an excellent tutorial about linear EXR outputs and workflows by OctaneRender artist Raphael Rau (Silverwing VFX).
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