http://fnordware.blogspot.com/2014/08/dwa-compression-in-openexr-22.html DWA compression in OpenEXR 2.2 "The default Compression Level setting is 45.0, which creates a visually lossless image that is often less than half the size of its truly lossless Piz counterpart. " So, I included it in my OpenEXR patch .... Not sure if you can call ILM library to do pixel format conversion so B44 will finally work? Time to more research!