Rob, It looks like there is either a bug in the D7100 firmware or since the D7100 is so new that the software reading the EXIF data is not up to speed. What program are you getting the EXIF data from? If the program is anything other than Nikon's then that could be the problem. It should say 52mm. However this is really almost a non-issue since it only tells you what the equivalent focal length would be if viewed on a full frame camera. What you could do is see if Nikon's View NX2 that came with the camera reports the same thing.