As we already said, the main challenge for digitization is the differencs between the rendering of information of your capture devices and your display devices. But here also appears another issue: what a regular user expects and what you are actually delivering away. In this sense, the problem here is that for the untrained eye your image might lack brightness or contrast or whatever factor of what they consider normal for a digital image (not to mention the settings that they might have in their displays, which might not necessarily be calibrated, etc., etc.). Since digital images are in fact representations that can be measured and assessed independently of what a human eye sees (and that's what we'll be describing in the next sections), you shouldn't care about your user expectations. Once you have scanned them correctly, images go in the wild and you can't control what users do with them. Your only option here is to maintain quality as much as you can.
Being said that, there are technical important aspects to consider about what digital images are by itself.
Digital images are measured in pixels, which esentially mean picture element. This is a concept that you need to bear with you, because basically all the misconceptions between resolution, quality, DPI and PPI come from this place. Digital images are NOT measured in inches. They are not dots in a paper.