The issue is not the spacing of the sensels, but their size. The sensels on an Epson see a big fuzzy spot. The higher the scan resolution, the more those big fuzzy spots overlap. Each one might still be subtly different, but at some point the fuzzy spots overlap so much that they don't add anything useful by being more plentiful.

If you evaluate the resulting file in terms of line-pairs/mm or MTF using a proper test target, then the spatial frequency of the fuzzy spots won't matter, as long as there is enough of them to fill in the gaps. All that will matter is the spatial frequency of the detail.

Someone already did this (was it Ben Syverson?), and found that the Epson does not provide a good modulation transfer at spatial frequencies greater than about 1500-2000 effective pixels/inch. But I do seem to recall that one still needed to oversample the negative to attain that outcome. So, it's reasonable to think we might overlap those fuzzy spots closely together and then summarize them into crisper spots using downsampling, or oversample and then limit enlargement to make sure we don't go beyond the scanner's capabilities. But I would never think that the scan resolution should be the same as what we expect the spatial frequency at good MTF to be. I routinely sample at 3200. Do I get more than if I sample at 2400? I dunno. But I'm sure that I don't get less, and it provides some resolution headroom so that I can be sure that I'm getting everything the scanner can deliver.

I also don't enlarge from Epson scans more than 4X happily. Let's do the math. If we get 1500 pixels/inch at good MTF, that is 60 pixels/mm, or 30 line-pairs/mm. If we want 8 line-pairs/mm in the print to provide the most sharpness a viewer can see even on close inspection, then we can print at 30/8=4x. If we set that standard at 5 line-pairs/mm in the print (which is as good as I can see in good light even with the bottom lens in my trifocals), we can go up to 30/5=6x. Most here are pretty confident in their Epson scans (at least in terms of resolution) up to a 4x enlargement, so my math lines up with that experience exactly.

But we still may choose to scan at a higher sampling rate as a strategy to ensure that we get the highest spatial frequency at good MTF possible. I really don't have a problem sending a file to the printer with a pixel density of 1000 or 1200 pixels/inch. My hard disk is big enough.

Rick "who often scans at 2400 and gets good 4x enlargements" Denney