Originally posted by RGlasel Good quality legacy lenses in good condition will still produce better images on better media, regardless of the camera technology used.
This is basically true for modern lenses as well. A quick look-see at the photozone.de lens tests for a particular lens with various sensor resolution bears this out. Almost all lenses will perform somewhat better for a given format with a higher resolution sensor. The exception being a lens whose native resolution is significantly crappy. Any improvement would be nominal in that case.
As for resolution of film images, they used to make something called microfilm. Microfilm pretty much represents the practical limits of silver halide emulsions. Kodak released a product for pictorial photography based on their microfilm product called Technical Pan. Tech Pan required special processing but was capable of providing incredible resolution to the point that it challenged the most capable optics of the day.
Nesster (site member) has a facsimile copy of a Modern Photograph article from 1978 where they attempted to determine the resolution limits using Tech Pan and other high resolution emulsions of the day. Here are the links:
How Sharp Can You Get? | Flickr - Photo Sharing! How Sharp Can You Get - continued | Flickr - Photo Sharing!
Short story is that even with careful technique and the best materials of the time (current age as well), film resolution for 35mm photography topped out at 105 lines/mm with Kodak High Contrast Copy film using a Leitz Summicron 50/2. The SMC Pentax-M 50/1.7 was not far behind at 102 lines/mm.
For comparison, here is a lens test for a recent vintage Summicron-M 50/2 on the Leica M FF, 24 Mpixel, digital rangefinder camera.
Leica APO-Summicron-M 50mm f/2 ASPH. Review & Rating | PCMag.com
Steve