Wet scanning was the default for drum scanners, the gold standard in the 90s. Essentially, you lay a drop of mineral oil on the glass drum, create a bond with the negative and then tape it down for good measure since the drum spun at a pretty good clip.

Wet scanning is worthwhile if you have a higher-end flatbed scanner like the Epson V700, 750 and 900(?) because they use higher-quality sensors and real lenses.

I almost bought a drum scanner a decade ago but would have to maintain a Mac Quadra for it to run. For large format film, a wet mount scan on an Epson V750 with VueScan software is great.

I suspect they're referring to "80% of what I want out of it," not "80% of the detail."

And I wonder if this is the scanning equivalent of wet lithography for making microchips?