Long time Nikon shooter here. Yesterday I witnessed my first ever set of corrupt NEF files. Made some images about a month ago on my Nikon D810, (NEF+JPG) and last night finally got around to transferring via card reader. Prior to the transfer all images looked great on the back of the D810. While the files were being imported into LR there were a handful of files that appeared normal for a second then suddenly became overlaid with bright rainbow horizontal bands. You can still make out what the images are. Not all the NEF's did this and the JPG's were good. After the import I put the corrupted NEF files back on the CF card and popped them into the D810 and sure enough the banding was there. So my question, is it possible a card reader can screw up an NEF file while it's being exported from the card? If so, is there a way to repair them?
I've seen this banding many times before. I'm guessing, but the transfer error may be due to a bad contact when you plugged the card into the card reader. Errors like this really can't be repaired, about the only thing you could do is try to transfer them again if you hadn't overwritten the memory card.
- Phil