here's a test report i'd logged. Somewhat disappointing news for the patriot. On re-reading, i now remember this pushed me toward the 25 f2 Zeiss, with pancake 28 2.8 Voigt' also an option.
http://www.photozone.de/nikon_ff/585-zeisszf2528ff summary appended below
i've no more to add to this entertaining thread :-) have a great week
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As a German website we'd love to report that we've seen another great Zeiss lens (home, sweet home after all) but at the end of the day the proof is in the pudding (or maybe in the "Kraut" here) and it just doesn't taste all that good. The Zeiss Distagon T* 25mm f/2.8 ZF performed pretty good in our Nikon APS-C review but it didn't impress during our full format lab tests. The resolution capabilities are simply sub-standard for such an expensive prime lens (@ ~800EUR/US$). The border quality is quite poor at large aperture settings. Same goes for the heavy vignetting here. The situation improves at medium apertures but the quality remains comparatively moderate. Lateral CAs are fairly low which helps a bit in terms of subjective quality perception. The amount of barrel distortion is about average for a prime lens in this class.
So, technically, the Distagon 25 is no doubt the weakest wide angle of the Z-family and it's no wonder that, according to the rumor mill, Zeiss considerd to redesign the lens. However, there's one feature of the lens we haven't discussed, yet.
The Zeiss lens is capable of focusing down to just 17cm (min. object to front element distance: 6cm) which is a fairly unique feature in an 25mm lens. It is this feature, that despite its optical flaws makes the lens fun to use in the field nonetheless. The unusual and unique look of close up images taken with a fast wide angle lens defines the niche where the Distagon 25 shines.
Just like the rest of its family, the Zeiss lens is built to the highest standards. Some users may complain about the lack of AF but, frankly, this is usually a non-issue for an ultra-wide lens. The focus confirmation is available in the viewfinder and in very critical (for example close focus) scenes Live-View can give you a helping hand.