scanning by canon multi function printer - large file size

hi there,

am using canon pixma mg2270 multi function printer. using the official canon driver for linux mg2200 series v3.80.
could scan/print under linux without problem

however for scanning the file size is much much larger compared with using under windows.

e.g. scanning a color document
under windows - default settings 300 dpi, a4 size, color, file size is ~1mb.
under linux - adjust to similar settings, 300 dpi, a4 size, color, file size is ~6mb.

and the linux scan output quality is just similar with windows scan, if not worse.

anyone having a clue? any settings to adjust? thanks.