Originally posted by Topsy In what case to corners really matter anyways? I don't have many photos that require extreme corner sharpness..
But to anybody who want's to save themselves from the frustration over corner sharpness when their K1 arrives, I volunteer to take care of your old glass for you. (will cover shipment)
Sharpness to corners matters when it matters. Your personal style may not require such sharpness. Others have different requirements. If you look at the work of Ansel Adams or Edward Burtynsky, you will find that sharp detail across the frame is an integral part of their artistic approach.
Before I retired I did a good deal of photography for museum exhibits. One of my last projects involved large format film work for backgrounds for dioramas, printed 12x15 feet. The project was for an internationally known designer who, of course, expected sharp corners. Much of that work was done well north of the Arctic Circle in winter conditions. The corners were sharp, even though at times I had to use my fingertips to melt frost from the corners of the ground glass to check focus.
These days highly detailed 2x3 foot prints are my most shown personal work.
Much high-end commercial work requires a high level of sharpness.
Please do not be dismissive of matters such as sharpness simply because they fall outside your personal stylistic universe.
In terms of older lenses, I've done quick tests of a good many on my A7r. A substantial number have performed at a very good level, including a number of Pentax lenses. I used a K 100 macro yesterday with excellent results. (My main MF lenses on the A7r are a nice little set of Leica lenses that I've used for about 30 years.)