Originally posted by gofour3 Exactly!
Phil.
A casual test I did of my 50mm lenses - including the 40mm and a 500mm mirror lens, using my K20D shows no significant optical advantages/disadvantages among the Pentax lenses as they are all limited by the 14.6MP sensor. I would consider the mirror lens to be optically challenged.
Full res version ->
Pentax Lenses 01
You can see how limiting the 14.6MP sensor results are when you compare to scanned film.
Full res version ->
Pentax SMC Macro 50mm f4 serie
And of course you can see from the optical enlargement in the far right how much more detail was captured on film using this lens that could not be resolved by my 4000dpi Coolscan scanner.
I have tested my Pentax prime lenses on film and I didn't find any that was significantly better or worse when it comes to resolving detail. As I said, I've bought all my manual focus prime lenses from the used market - condition unknown and cheap, so perhaps I've just been really lucky?