As you can image, and predictably, the lens is phenomenal and possibly the best 50mm (yes, it’s 55mm) lens ever made for an DSLR.
Here in Germany the "fotomagazin" jounal has made a test and review where they say that the Sony/Zeiss Sonnar T* FE 55 mm F1,8 ZA has a better IQ at 1/4 of the price.
I don't get 100% through their test methods to see if they did something wrong but the results are hard to believe as the optics are comming from the same source.
I think everyone is missing the entire point of this lens and all of the information about it.
50mm lenses have been completely dominated by the the double gauss (planar) design for the last 70+ years, which severely limits image quality at fast apertures. It's a very poor archaic design that results in around 4 times worse performance in every image clarity measurement, with the only upside being a slightly more compact design. There is literally no planar lens that performs even passably well wide open. The Zeiss Otus was the first retrofocal normal lens for full frame cameras and it showed there was a night and day difference compared to the double gauss design. The Sigma 50mm ART will be the second. The 55mm f/1.8 ZA I'll address later.
Planar lenses have extremely poor performance wide open, lets use the lens rentals 50mm comparison as an example ( http://www.lensrentals.com/blog/2012...-50mm-shootout
), which tested 23 planar normal lenses. At f/1.4 planar lenses achieved scores in the 300s and 400s in that test for average MTF50 resolution. For comparison the Zeiss Otus delivers average resolution of 800. That's just under 5 times more spacial resolution than the lens it supersedes, the Zeiss 1.4 Planar, @ f/1.4. (remember we have to square linear resolution data to get normal resolution)
If you look at other points of comparison you can see that planar 50mm lenses scored poorly in haziness/glowiness and purple fringing, and often scored poorly in chromatic aberration, usually by a factor of 3-5.
Zeiss decided that it was impossible to make a good standard prime using the double gauss design, after all the design forces a lens to be short and leaves little room to correct aberrations. So to make more room for corrective lens elements, Zeiss switched to a retrofocal design, which means that the lens is actually longer than it's focal length. They more than doubled the number of elements which allowed them to finally make a good 50mm prime, for SLR. Previously this had been an impossible achievement with the majority of standard primes having camera phone resolution wide open.
The 55mm Otus is a very special lens too because it's Apochromatic, which means it has no purple fringing all other primes in this range have a ton of purple fringing that looks very ugly, and most publications won't allow you to submit photos with any hint of purple fringing.
There is no prime that exists that's f/2 or faster below 150mm besides the Otus that doesn't have ridiculous amounts of purple fringing. As a professional image editor for magazines purple fringing was my mortal enemy so this is a huge deal. This is a feature that isn't found on any lens below the $2000 price point, (Exception being the Sigma 150mm APO which is slightly less, and when certain lenses go on sale). And this is a feature isn't found on any wide, normal or telephoto lens that has a fast aperture.
So the 55mm Otus is special because it breaks the mould for standard focal length SLR optical design, it's the first and currently only available retrofocal standard fast SLR lens and it's the only non super-telephoto fast APO lens in the world.
The Sony 55mm f/1.8 ZA is not an SLR lens, it's a mirroless lens. Making the Zeiss Otus was an endeavor much like getting a man to walk on the moon. It's an incredibly achievement to overcome the limitations of standard fast SLR lenes. The mirror box is what prevents standard lenses from being good, and it took 70+ years to solve the problem. The Sony 55mm f/1.8 ZA is an endeavor as complex as getting a man to walk on the sidewalk, it's one of the most basic lens you can make, and it's not APO. It's as special as McChicken sandwich.
Hopefully that puts everything into perspective. This is a very special lens, which more than doubles anything in it's class. The Sigma 50mm f/1.4 ART is going to be equally special with 89% the performance, although lacking APO, but also doubling the performance of anything else like it.