Convert nef to pnm Online: nef2pnm

You can use Tom's Editor to easily convert images from
Nikon Digital SLR Camera Raw Image File .NEF to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

NEF

Nikon Digital SLR Camera Raw Image File is an image format with extension NEF.

PNM

PNM images are uncompressed 24 bit RGB images. Can cannot store Alpha channel. PNM images come in 2 types: binary and text. Especially popular on Linux.