Thanks Tina and Richard for your comments.
I wanted my scanned files saved in NEF because I thought the size would
be smaller than TIFF. But I am mistaken. So, I'm saving them now in TIFF.
Tina Manley wrote:
NEF files from the Nion scanners are not meant to be opened or worked
on in anything besides the Nikon scanner software. It's just a way of
saving the scans and their information until you can work on them
later and resave them as tiffs or jpegs. Open your scanner software
and you'll be able to work on the NEF files.
Tina