A. Scanned images are stored using industry standard Group Tiff file compression. This is white compression, which means the white is thrown out and the black plotted in binary code. So a page with a lot of writing on it or a grey or coloured background will have less white space and will be greater in file size. Having said that, on average you can get in the region of 25,000 A4 images on 1Gb of hard disk storage which, in plain terms, is about two and a half four drawer filing cabinets. PDF images take about the same amount of storage space.