Well, perhaps someone else is investigating the lens question too, but everyone I know associates it with the artist David Hockney, and his book. What makes it interesting--unlike discovering that maybe Faulkner used a thesaurus--is the observations, from the point of view of an artist, and one who draws pretty well. He thought he recognised Warhol's line quality in an old drawing, a swift, super-confident line (Warhol traced from a projector). If you know Hockney's rapidograph ink drawings and how hard they are to do, you can see how he'd be sensitive to that. And he got interested in it, is still learning about it, and how to do it--it's not really easy to use--and he makes it an interesting case. A sidelight interest is how the best eyes in the field of art history can have been so unobservant, how much resistance there has been to considering the question today. (The use of lenses was apparently associated with occult, by the church, and so open reference to it was inhibited, although there were some remarks about artists who only paint in dark cellars.)

Otherwise, at least for me, it'd all be very tedious, since I grew up with photos, can't begin to imagine the excitement artists once felt for perspective as a device, and have re-learned perspective drawing almost as many times as I've forgotten it again. Aesthetically, I've never experienced How did they do that? in regard to the chores of technique. It's just like how gymnastics-dance routines are so sad and lugubrious, compared to, say, dance. Or those singers who use every song as an excuse to practice their scales. Bleah.