Format used my Sigma SD9 and SD10 digital camera. 

Official spec: [[http://www.photofo.com/downloads/x3f-raw-format.pdf|http://www.photofo.com/downloads/x3f-raw-format.pdf]] 

But the RAW data is "encrypted". dcraw has code in GPL but no documentation per see.  [[http://www.photofo.com/x3f-raw-format/|http://www.photofo.com/x3f-raw-format/]] is a project to try to document this.