I know it has been over a year, but I hope you've discovered the solution. I also have a D7100 and use the "lightening/USB adapter" for downloading "ALL" formats of photos from camera to my iPad mini. I mostly shoot in RAW myself. The process I used was: turn on ipad, open photos, plug camera into iPad port using adapter, THEN turn on camera. The iPad will immediately bring up photos for import. You can then download all or select which ones to download. At the end of the download process you can also decide to delete photos off the camera card. I usually keep them on as I process them later in Lightroom. I will start using the WU-1a wireless adapter for quick downloads of jpeg photos for immediate sharing from the "field" environment and as a remote using a smart phone. Hope all has turned out well for you ... that D7100 is a fine camera 🙂