I have spent a little time (too much) examining nagatives and slides
under a microscope, and found that there is a great deal of detail
that simply does not come out with normal digital printing you get at
most photo labs. A small object I can see on a negative will appear
as pixels on a print or .JPG file. I don't know what resolution is
required to get all the information, but I suspect it's not far short
of 4000 dpi.