In September 2014 Zeiss presented two new "Loxia" lenses for Sony's A7 full frame E-Mount series. The Loxia 2/35 and 2/50 are dedicated to manual focus shooters looking for high image quality in a compact housing. In this short review I will oppose the Loxia 2/35 to the ZM Biogon 2/35 for M-Mount rangefinder cameras.
If you compare the lens design to the Zeiss ZM Biogon 2/35, you will find a lot of similarities which seemed to induce some discussion on the internet if this is just a recycling of the ZM Biogon elements and design, which produced disillusioning results when adapted to Sony's new A7/A7R full frame series with blurry edges and strong field curvature.
The following shots were taken at open aperture (f/2.0) with both lenses on the Sony A7R. Both were focused at the part of the tree most nearby the image center (see the "focus X" mark). There was no lens correction profile applied, both images were developed from RAW with the same settings.
Zeiss ZM Biogon 2/35 at f/2.0 adapted to the Sony A7R (using a Novoflex adapter):
(you can click on the image to see other sizes)
This is a 100% crop (actual pixels) from the upper right edge:
You can see strong vignetting and a lot of edge blur mainly produced by field curvature.
Now the same scene wih the Zeiss Loxia 2/35 at f/2.0:
(click on the image to see larger sizes)
Again a 100% crop (actual pixels) from the upper right corner:
You can see that there is significantly less vignetting and much better sharpness in the corners. The extreme corners are still not perfect at f/2.0 but if you stop down a bit (which you would do anyway in such a situation), everything is fine.
Compared to the Zeiss FE 2.8/35, the Loxia gives you one stop more light and more options to play with depth of field (DOF). The Loxia 2./35 renders a pleasing bokeh, as you can see in the following examples:
(Zeiss Loxia 2/35 at f/2.0 on Sony A7R, no lens correction profile applied, click on the image to see other sizes)
(Zeiss Loxia 2/35 at f/2.0 on Sony A7R, no lens correction profile applied, click on the image to see other sizes)
Conclusion
Although the Zeiss Loxia 2/35 uses a similiar (and proven) lens design like the ZM Biogon 2/35 (designed for range finder cameras), it is distinctly and visibly better optimized to requirements of the Sony digital A7 / A7R sensors. They provide good image quality in a compact size and the manual focus as well as the "declickable" aperture ring make them a very interesting choice for video shooters as well.
You can find additional information about the Loxia lenses here: http://www.zeiss.com/camera-lenses/en_de/camera_lenses/loxia/loxia235.html