can you try:
scanimage --x-resolution 600 --y-resolution 600 > si-600-600.pnm scanimage --x-resolution 600 > si-600--.pnm scanimage --y-resolution 600 > si---600.pnm
can you try:
scanimage --x-resolution 600 --y-resolution 600 > si-600-600.pnm
scanimage --x-resolution 600 > si-600--.pnm
scanimage --y-resolution 600 > si---600.pnm