If one is going to benefit from old slide and negative resolution, scan
at the highest resolution your system can handle. Some amazing detail is
available in some of them. Store or archive them in that highest resolution.
Store on CD or DVD disks. Then when one wants to post to newsgroups or
internet sites, you can downsize copies for posting if that's what your
intended viewers want. BUT, keeping the high resolution scans makes it
possible to clip out portions of the original picture, magnify the clips and
find great history in the details!


What he said, plus...
Make certain that you save the file in .tif format.
When you resize for posting the web, save that image as a .jpg.