Yeah its probably using zlib for compression. If you're distributing and packing the item into a zip you're better off not compressing and letting winzip do it for you. people always make that mistake with jpgs. They think making something a jpg then stuffing that into a zip will double the compression. In reality they only gain a few percent and that is from compressing the header in the zip. Now I don't what they are doing with compression with the propack but I would think it would be a boon if they tokenized the cr2 so it didn't have to parse the thing upon loading. That would be a great speed up.