I edit a NEF file in ACR5.3 and when I open it in Elements, the NEF file reflects the changes I've made in ACR. So I can get back to the original NEF file, before the ACR edits, I decided to first save it as a dmg file. I can find the dmg file in Windows Explorer, but I can't do anything with it. How do I access the dmg file and make use of it? Many thanks.