Same here I already mentioned it in the forums. Firefly is of no use in Poser 13 renders get horizontal cuts and gets squished together you can even see the lines. so not a gamma issue like in superfly it is simply a broken render engine ! 

Firefly in Poser 13 of no use you need to use a older Poser version for that feature !

Also the final render after saving in Firefly is of less quality then a firefly render in poser 11 you see this when you enlarge over 100% with same settings.