Convert x3f to pnm Online: x3f2pnm

You can use Tom's Editor to easily convert images from
Sigma Camera RAW Picture File .X3F to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

X3F

Sigma Camera RAW Picture File is an image format with extension X3F.

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.