I'm used to working with older versions of Photoshop CS, where I 'just save' exr with no options. This previously resulted in file sizes half that of .hdr. In this latest version if I choose to save uncompressed (which I assumed the old versions of Photoshop did?) the file size is a good 10x larger than they used to be. If I save as zlib or wavelet, they're similar size (a fair bit less than a .hdr).
What did the old Photoshop use for compression? Or how can I find out? I don't remember my old exrs taking so long to compress and save either (with zlib) but I might be wrong.
I'm not saving any transparency either (that I know of!).
It probably used the basic zips compression like 90% of all EXR implementations. Not sure, though. I prefer using TIFFs or PSDs directly for working on 3D rendered images, the rest I do elsewhere...
Previously Photoshop always used the wavelet compressor for EXR.
And Zlib can be very slow, and very data dependent.
It's safe to say that PsCC doesn't have full support for EXR or partial support for EXR 2.0 ?