Comparison with Tamron 17-28mm f2.8 I must suggest picking up:
-) the Tamron for focal range, starting also 1mm wider and with more close up possibilities, along with overall great quality.
-) the Batis to obtain even higher quality in the details regarding control of aberrations and less distorsion, accepting the restriction of a single focal length.
[Tested on 36 MP camera] is an excellent ultra-wide prime lens. Most of the image frame is already very sharp at fully open aperture although there is a bit of softness in the far corners. The corner softness is gone at f/4. [...] Very low lateral CAs and marginal field curvature also contribute to the very high quality [...] Vignetting which is on the very high side. Highly recommended.
[Tested on 42 MP camera] Apart from huge vignetting level on full frame, it didn’t have any significant slip-ups [...] the lens didn’t show any spectacular results either. [...] Both optically and mechanically, the Batis 2.8/18 is a solid construction. It can provide very pleasant images characterized by good sharpness in the frame centre. The only flaw we found is the image quality on the edge [...] even on stopping down.
[Tested on 42 MP camera] It really delivers as a light, portable, and yet optically exceptional lens. It does have some weaknesses, such as distortion and vignette, but a software profile does a good job of eliminating those. The extreme corners aren’t quite as sharp as the center, but they stand up compared to competitors.
[Tested on 12 MP camera] This is a very good lens with no real flaws. The optics are great (at all distances and aperture values), the build quality ins’t bad either and the coma correction is really outstanding. [...] While the lens is really lightweight it is also quite big, especially with the lens hood,
Sony Alpha Blog
[Tested on 42 MP camera] It is developing very good performance for a wide angle; stopping down to F4, it will give its full potential: optical issues are all very well corrected automatically by Lightroom, the lens is small, discrete and quiet in video, clor rendition and constrast is superb and carry the Zeiss signature. A very nice lens for architecture and landscape!
[Tested on 12 MP camera] Vignetting is pronounced but not overly distracting [...] Aberration and coma performance is nearly perfect straight from f/2.8, and I left it there for every astrophoto in this review, seeing no need to ever stop down. [...] It is simply the best wide angle lens I’ve ever used and a perfect choice for landscape astrophotography. Highly Recommended.