As I have an old CanoScan LiDE 30 and troubles under Ubuntu with SANE I have to use scanimage. It is know as as

scanimage --help
-- last line --
plustek:libusb:002:002

To scan a A4 which is the standard paper size over here is need to use

scanimage -l 0 -t 0 -x 215 -y 297 --resolution 150 > myimage.ppm

Problem's I have so far is in the output size of the above line. The mode defaults to color so the scans are huge.

scanimage -l 0 -t 0 -x 215 -y 297 --resolution 150 --mode Lineart > myimage.ppm