> Space age lenses were significantly lower resolution than the film.

Can you say a little more about this? Modern lenses boast about 7-elements or aspherics, but does that actually matter in prime lenses? You can get an achromat with two lenses and an apochromat with three. There have definitely been some advances in glass since the space program, like fluorite versus BK7, but I'm wholly in the dark on the nuances.

I find modern primes much sharper than their older counterparts not because of the elements or the optical design, but from the glass directly.

Sony's "run of the mill" F2/28 can take stunning pictures, for example. F1.8/55ZA is still from another world, but that thing is made to be sharp from the get go.

The same thing is also happening in corrective glasses too. My eye numbers are not changing, but the lenses I get are much higher resolution then the set I replace, every time. So that I forget that I'm wearing corrective glasses.

I wrote a longer post a few months ago.[1] The tl;dr is a) computer aided design and manufacturing b) aspherical elements c) fluorite glass d) retro focus wide angle designs and e) improved coatings. Mirrorless lenses also beat slr lenses because they are much closer to the film plane — of course rangefinders and other classic designs never had this problem to begin with. 1: https://news.ycombinator.com/item?id=42962652

Edit: this is just for prosumer style cameras. If you look at phone sized optics that’s a whole other ballgame.

The lenses also have to be better to compensate for the smaller sensors. All lens defects get more "magnified" the smaller the sensor is. So a straight comparison isn't fair unless the sensor is the same size as the film was.