ps to iff conversion does make sense only if you are attempting to recover graphics assets from PostScript documents (.ps) to Amiga Interchange format. Adobe graphics software are your best choice in this since these tools can import PostScript files, as for export to Amiga IFF format. Certainly doable in some versions of Photoshop, but maybe you have to rely on a middle step conversion to a common PNG/JPEG format and then use another tool to create IFF variant of it.
Updated: August 29, 2023