[Guest]

A couple comments:

 

* "proper" lenses can perform better in the corner than in the center, there is no rule against this.  If the edge of the image field is weighted higher than the center of the field any CAD software be it Zemax or Code V or HEXAGON or OSLO or some other will produce a better corner image than center one. 

 

In a theoretical context, if you perfectly correct coma astigmatism and polychromatic aberrations but leave spherical aberration, a lens with any amount of vignetting will perform better in the corner than the center, since the vignetting will eliminate the most poorly behaved rays.  Not that they are poorly corrected, but this is the case with a couple of nikon's supertelephotos.

 

The ZA 135/1.8 does have quite a bit of axial color, I would imagine based on the results that one of two things is the case:

 

* The review website has a bad copy which is relatively unlikely to have happened twice and the lens is out of alignment

 

* Or the lens is focused better in the corner than the center indicating that there is some field curvature and the center is backfocused.

 

Hey, maybe that will be a new trend in lens design - sharp in the corners and mush in the center. You can call it the 'Anti-Holga'.

 

As for the ZA 135/1.8, I'm just basing it on the PZ review:

http://www.opticallimits.com/sonyalphaff...ff?start=1

 

(Even though PZ doesn't test at infinity, I still say that in the comparison it looks like it is back focused.)