Many people having an Epson V700 don't know what that machine is able, because not having adjusted media height or ensured flatness, or not knowing how to make the refined sharpening Epson scans require in post, to obtain the best result while totally avoiding overshot.
Les, see the table at the bottom, and you'll see that that test is not that arbitrary, but a good example of the reality.
Since many years ago RA-4 darkroom printing has been declared near extinct, almost nobody prints RA-4 optically. Priority has been scanning since the digital minilab era in the 1990s. What % of the RA-4 prints are optic? one in one million?
If you observe color negatives of the pre digital minilab era with a microscope, at (say) x400 you may see that the image structure (color clouds) changed compared to color negative film made in the digital minilab era.
See this table:
View attachment 253167
Reference:
http://www.tmax100.com/photo/pdf/film.pdf
These are results from contact copies. Amazingly the 40 years old VR100 (The kodak product that introduced T-Grain in around 1980) has the best rating of the color films, but it had some grain and more color noise in the scanning. If you make clouds larger then clouds from a color layer overlap better with clouds in the other layers, lowering color noise in the discretization.
There always had been a trade between size of color clouds vs granularity, a film that scans easy may require larger color clouds, at the end lost sharpness can be compensated with a wise digital sharpening. Of course a detailed analysis should consider what average cloud size we have for each density in each layer, measured in the reticle of a microscope... but to compare it's enough to inspect at x400 how gray subjects with same density (concrete buildings, for example) have the clouds overlaping less or more.
In the other hand that contact test suggests a resolution value in ppi, this is 3300 to 3700 for the old Portra variants, but those are tests from contact copies, those figures have to be lowered for practical shooting conditions, the same document calculates the actual ppi once the lens performance has degradated the image, note that Portra 160 was peaking 2450 with a very good 140 lp/mm lens:
View attachment 253169
This fully explains why an Epson V700 is able to get all IQ Portra 160 is able to record, as it is able to resolve 2900dpi effective in the Hor axis and 2300 in the vertical one.
I guess this table is a precise answer to what OP was asking.
Then you might also be interested in articles posted at
https://clarkvision.com/articles/index.html
A good reference between film and digital with a lot of studies related to resolution.
There are several things that are highly problematic with those articles.
First of all, it's important to take the meta perspective and remember in what kind of air and time these two texts where written.
Digital had taken most photographically interested and involved people by surprise, with the rapidity, with which it was suddenly replacing film as the image capture medium of choice.
Therefore you had the choice of either appearing to be a luddite, behind the times, desperately clinging to the old "paradigm".
Or go full on with the "new stuff", while still appearing to make a "mature carefully judged and weighted decisions of when and how".
Furthermore:
There was (and still is) also a lot of confusing the then still steadily marching Moores Law with equal development in sensor technology.
Moore’s Law is the main driving force behind all the personal computer technology we have seen advancing rapidly since the seventies (some would argue it’s the only driving force).
Improvements in CMOS and CCD has very little to do with Moores Law however.
In fact the actual sensors have only seen quite small incremental improvements in the basic technology and material science and QE in the last fifteen or twenty years.
The main improvements being in much better post processing and some minor improvements in amplification strategy.
Thirdly, most of the scanners of "back then" was made to scan to computers that had smaller resolution displays (megapixel monitors mostly over narrowband internet), less RAM and less need for resolution in general.
High resolution prints was something for professionals, "fanatics", and large colour prints was still possible with darkroom RA4 if you really needed it (still is if you are dedicated, or know where to go).
Clarke has a few examples from a drum scanner. But we know nothing of it’s calibration or other circumstances concerning the scanning.
With that out of the way, the articles themselves are technically and semantically dubious in a number of ways.
There is much weasel wording and handwaving, where the authors think they can get away with it.
There are no concise parts part about method, or any rigorous references to other works or sources to speak of.
These are not scientific or academic peer reviewable articles (and they don't purport to be), though I guess for many people they give off an academic air, that impresses and appears to have special authority, due to the authors clearly being used to writing academic papers.
Tim Vitales article while interesting in a number of ways, appears to be mostly a scrape of other papers and articles, with little work done by the author himself.
Tim Vitale is a conservator who specialises in photos. That does not tell us much about his technical authority.
Clarkes article has a number of gross inaccuracies, omissions, lack of clarity, forces conclusions and frankly seems biased (perhaps for the reasons I mentioned to begin with).
That wouldn’t be such a problem if the two articles weren’t among the first that pops up with a google search, and if they didn’t still get cited time and time again.
There have been several examples or hints at just how much resolution is in a square inch/mm of film in the intervening fifteen years.
Here is a two examples;
Tim Parkins tests are pretty famous. Here is one of the more interesting images from one of them (in this context) from his, “film against a Phase One 80MP back”, test.
Don’t pay any mind to the changes in film size between examples, as long as you compare the same size against itself, you are good.
The emulsion is if not exactly the same then much the same between 135 and 8x10.
What matters is the dpi of the scan and the magnification.
Notice how close Portra 400 and Tmax 100 really is in the Mamiya 7 microscope crops (while the structure certainly looks different).
Also notice the jump from 4000dpi to 8000dpi, and how much is still left to resolve in the microscope examples from the same piece of film:
Here is a another good example of how much resolution it is possible to get out of film, and this not even with optimal equipment.
IE “only” a 5400 dpi scanner and less than optimal film to show resolution:
http://www.rokkorfiles.com/7SII.htm
Notice how you can see the individual minute marks on the clock face!
This is far, far from the 2600dpi claimed by 138S and authors of the articles as the practical limit for colour film.
