Sips not working with pict, qtif and sgi files
Not the definitive answer but be careful with sips. It seems to me sips itself has been updated but the man page remained the same. On my Mac PICT creates no output at all and PSD creates a file that is totally garbled when viewed in Photoshop. It seems you can also export to PDF, and the result opens just fine in Adobe Acrobat, but when opened in Photoshop or Illustrator what you see is very, very different of what should be there ...