I didn't remeber who Richard Crisp was until I visited his homepage again. That was a page I visited very often in the beginning of 2010s, he inspired me to look for medium format lenses. At that time he didn't own a Pentax 6x7 400 mm ED IF.
I looked at the photos now but I see most of them are cropped so it doesn't tell how the lens behave at the edges.
Earlier I owned a Pentax 6x7 165 mm f/2.8 lens, almost no vignetting at all even at f/2.8 when used on a full frame camera. But it had some cromatich aberration problem. The only of my lenses I could use at f/2.8.
http://www.astrofriend.eu/astronomy/...vs-pentax.html
Today I made a new shim and placed it in the baynet:
http://www.astrofriend.eu/astronomy/...645-300ed.html
See at bottom of page. If I'm lucky the tilt is now eliminated, maybe there will be a clear sky tonight so I can do a test.
/Lars