A digital sensor can produce an image on the computer screen that looks essentially like a film radiograph. However what makes a digital image superior is not the fact that it looks like a film but the fact that it is digital. That means you can use a computer to store, transmit and enhance the image.
Each picture element or pixel on the monitor can display one of 256 different shades of gray. However the average person can only distinguish about sixty shades of gray. (A trained radiologist can distinguish around 100 shades.)
Since we can not distinguish the difference does it matter that the image has more data than we can see? Is that data wasted?
The answer is yes it matters and no, the data is not wasted. However in order to use the data to aid in diagnosis the user needs to employ image management software to enhance what we are seeing.
This is an excerpt from The EOT Guide to Digital Radiography