I’ve been asked to compare the Sony 20mm f/1.8 to the Zeiss Batis 18 mm f/2.8. Here’s a test with both lenses mounted on an a7RIV aimed at a low-contrast Siemens Star at about 8 meters for the 20, and about a meter close for the 18, with the star in the center and the lower left corner. I used AF-S with the small spot. In each case I made three shots at each setting, focusing anew for each shot, and picked the best. This method calibrates out focus curvature. Developed in Lightroom with sharpening set to amount 20, radius 1, detail 0, which is quite a bit less than Lr’s default sharpening. White balanced to the gray surround of the target. They are presented at about 250%.
The difference in focal length appear to be more than 10%. The Batis has similar extinction resolution , but lower contrast.
The contrast is getting closer.
In the corner:
The Batis is sharper, abut has a bit more light falloff.
The Batis is still ahead, but the Sony is catching up.
About the same.
The a7RIV was unable to focus the Batis in the corner here, so I don’t think we can draw any conclusions from this last pair.
At four or five hundred dollars cheaper than the Zeiss lens, and a stop and a third faster, the Sony 20/1.8 looks attractive here.