Hi All,
First off, thanks so much for the feedback on this post. Really incredible and smart people here.
I decided to run a F-Stop test. Used a Pentax 645Z and a Pentax-D FA 645 55mm f/2.8 lens.
Shot from F-4 up to F22 using the hyperfocal marks on the lens barrel aligned to the center of the infinity mark on the lens. A bit hard to tell if I was perfectly aligned but all the shots seem focused so so far so good.
Here's what I did:
1) Used a tripod and shot across a bunch of fstops in AV mode.
2) Shot in RAW
3) Brought all the images into Photoshop Camera RAW and did an identical "auto adjustment" to all images.
4) Applied no sharpening anywhere (Camera RAW sharpening set to zero.)
5) Brought the image into photoshop and here's what I got.
LINK TO DROPBOX file where you can actually see this image.... It's resized as the master was over 1.5 GB as a TIFF. This is 44mb.
http://tinyurl.com/p6r9svg
Based on what I'm seeing, F22 looks pretty darned good. And to clarify, I literally didn't focus any of these shots with the LCD or viewfinder.... Just lined up the hyperfocal f-stop to infinity.
Plan on more testing. But F22 looks quite encouraging. Again, no sharpening was applied to any of the images.
And I'm not seeing a lot of diffraction at F22.
What do you think?
All the best!
S