Originally posted by jawats Since all of these manual focus lenses are no longer available new, it is entirely possible you may find them in great shape for under $100. The SMC-Pentax-M-50mm-F4-Macro lens I found on a local CL - with a bunch of others, for so cheap I wondered if it was any good at all. But after using it for just a couple of rolls of film, I quickly noticed how particularly sharp it was and wondered just how good it really is. Below is an example from Fuji RVP (original Velvia) scanned at 4000dpi.
Click for larger version Fuji RVP
I got curious just how high resolving and sharp is this lens that I setup controlled testing using my 14.6MP Pentax K20D as well as scans of Kodak Techpan.
Click for larger version SMC-Pentax-M-50mm-F4-Macro lens test
Clearly my 4000dpi scans of Kodak Techpan outresolve my K20D's sensor. To the far right, I optically zoomed in about 4.5X using my autobellows + 50mm f4 macro and you can see how much detail was actually captured on the film.
To take this a step further, I used a Nikon D800 to "scan" that frame of film and it still is not enough to fully resolve the details captured. Actually, not even close since it is about the res of my 4000dpi scans.
Click for larger version Kodak Techpan 04-27 scan compare
So if you need a high resolving macro lens, this is a good candidate to consider if the price is right for you. Unless there is something wrong with the copy you get, it will not be the reason you cannot resolve the finest details in the shots you take.
BTW, I also got the 100mm f4 macro and it is also an outstanding performer. Gives you more distance to your target.
---------- Post added 02-21-18 at 03:22 PM ----------
BTW, I did similar testing with the following lenses too. Of course I now know these are all limited by K20D's 14.6MP sensor in terms of resolution but it is a quick guide until I get around to assembling the Techpan shots I've done and/or perhaps using a K-1 to test with.
Click for larger version Pentax Primes+