When you select Professional Mode, you see the Epson Scan Professional Mode window.
Documents or photos: Placing Documents or Photos
Film or slides: Placing Film or Slides
If you selected Film (for scanning film or slides) as the Document Type, click the arrow in the Film Type list and select Positive Film, Color Negative Film, or B&W Negative Film.
What happens next depends on how you started your scan. See Finishing the Scan for instructions.