[Tatouzou]

Interesting. Personally, I've found screwdrive to be amazingly accurate. The fastest AF lens I own is the FA50/1.4 - an old design by today's standards, but ever since I got the AF fine adjustment set up just right, I rarely get inaccurate focus with it on my K-3 and K-3II even wide open. I might occasionally get missed focus because of a poorly chosen target, but with a well chosen focus point, it's bang on all of the time. I'm prepared to believe screw-drive isn't as accurate, and I can certainly see why micro-adjustments from SDM, DC and other electronic drive systems could be more accurate than electro-mechanical. That hasn't been my personal experience, though...

I too find screwdrive AF to be quite snappy, efficient and accurate, even more on recent cameras from K3 on, which have a more powerful engine.
But, with 24 MP sensors, screwdrive lenses more often need an in-camera micro ajustment to get the same focus accuracy as in live view.

FA 77 and FA31 are my son's (Nicolas06) most used lenses. Go to his flickr gallery (he also posted some of them on this forum) and you will find a lot of his work with these lenses, that are right in-focus and amazingly sharp at pixel level at large apertures on 24MP K3, whose pixel density is higher than K1.

[Nicolas06]

Everyone here wants to believe it's not the case, but the older designs don't have nearly the resolving power of the new ones.

We all know that the biggest issue for our photos being not good enough, in particulary with Pentax lenses is the lack of resolving power... of course.

The full image:



In attachment, the 100% crop. If you see that 1024 crop on a 22" monitor in full HD, it will fit 1/4 of the screen. It means that the full image if you were to print that size would be 6 time bigger both horizontally and vertically. So that would do a full screen on a 65" TV monitor, in portrait mode, of course. 65" in metric system is 1.65meter.

And the problem is not the lens couldn't do better, the problem, the sensor is only 24MP without pixel shift.

The problem isn't how it is going to look on a 65" form 10" because nobody ever going to check that. The problem is how it is going to look printed in 4x6, how it look on facebook, on a photobook, on a double page in an art magazine, in a galerie in 20x30", on the familly TV from 3 meters away, on the 2MP computer screen or 3mx4M billboard from 20meter away.

The problem is this is f/4, and a good share of the subject is out of focus anyway if you zoom too much...

The problem isn't to know if the modern (ready big, huge, stay in the drawer designs) have more resolution, but more if what we have already is good enough... And if other criteria like size/weight, actual rendering, subject pop etc aren't more important than to see the skin imperfections in more details in pixel shift on an hypothetic 50MP APSC that doesn't exist to get enough resolving power to maybe out resolve the old lens design.

[cali92rs]

My vote is for a very sharp 20mm f2.8 or f4 to complete my 31/77 trio.
That is all