Epson V850 scanning and print size help

[Deleted member 88956]

I do not know what the V850's actual optical resolution limits are, but I am confident that they are significantly less than 6400 ppi (pixels per inch).
More likely something around 1800-2400 ppi.
So right from the beginning, a scan performed at the setting of 6400 ppi gives results that are about 1/3 from the data derived from the negative, and 2/3 interpolated from the data derived from the negative.
The quality of that interpolation process depends on the quality of the algorithms built into the software. In many cases, the result will be an excellent facsimile of the original data in the negative, but it also may differ from that data, because it is based, inherently, on assumptions.
A better scanner, with higher optical resolution, provides more data to the software, which generally results in more accurate facsimiles.
A measurement of the "quality" of the results, when printed large, will be a highly subjective measurement - and will depend a lot on the talent, knowledge and skills of the people who expose the film, develop the film, use the scanner and digitally process the result for the purpose of preparing a large print. Each stage of the "workflow" requires a significant amount of care and skill, and each stage can serve as a bottleneck to fine results if that stage is not performed properly.
When it comes to the technology, I would say that the Epson V850 is probably capable, but not ideal. The better technologies aren't cheap or easy to access.

Well said, 100% agree.