I had a problem this morning where all of my lightroom pictures under a certain category disappeared from lightroom after I saved them to a Seagate drive. This happened once before. After tearing my hair out (what is still left!), I realized that in my process, I somehow changed the name of the category by one letter in Finder. When I replaced the letter, my pictures magically reappeared in lightroom. Problem solved. However, when I downloaded new pictures shortly afterward, they all came in as DNG rather than NEF. In my quest to solve the first problem, what did I hit to make that change? I now want to go back to NEF. Any clues??? Thanks.