image capture

I had been using Image Capture with my Mini as the Epson Due Scan software on my old Epson Perfection 4180 Scanner didn't seem to work. Since I bought an iMac I downloaded the drivers from Epson for VueScan and it works fine.

I just scanned a 2.25" square B+W negative with image capture that is about 13 MB then scanned the same neg and settings in Due Scan and the file is 3.5MB and just a hair sharper. Any ideas why the difference in end result file size ?

Both are TIFF files and saved in Photos.

thanks for any help