GrahamWelland
Subscriber & Workshop Member
I don't hesitate going to f/16 if corners are important.
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My copy is less sharp at f/16...I don't hesitate going to f/16 if corners are important.
Worth pointing out this is possible on any major tech camera. On an Cambo or Arca you would simply rotate the digital back mounting plate 180 degrees.@Sarnia - since you're using an Alpa, you have the option of mounting the lens in any of four orientations. So, if you're still having issues with corner performance, rotate the lens 180˚, reattach it, and shoot the same scene again, and see if the corner performance is identical or has 'moved'. If it's the latter then there may be an issue with the alignment of the front and rear groups.
The 24/4 ULD fisheye (Mamiya manual focus) covers full frame 645 and when de-fished, behaves just like a rectilinear 24mm lens. It's very sharp at all apertures, but does show lateral colour (however I think it's no worse than the 28mm excerpt that Torger showed above, which rather shocked me for a lens of that price and complexity). The lateral colour cleans up well in any software for automatically registering the 3 colour planes geometrically. Corner sharpness drops a bit too with de-fishing, due to re-sampling and stretching of the PSF (...but again, the 28mm corners I've seen are not that hot either). And there's zero vignetting, and no mucking about with centre filters.There are some very nice medium format wide angle SLR lenses made but I think only the Mamiya / Phase 28 covers full frame 645.