Zeiss Batis 18mm f/2.8 Distagon: Data Sheet Confusing Because Distortion Graph is Software-Corrected (only)
In the Zeiss Batis section of Guide to Mirrorless, see my discussion of distortion for Zeiss Batis 18mm f/2.8, along with real-world examples in my Review of the Zeiss Batis 18mm f/2.8 Distagon.
The Zeiss data sheet for the Batis 18mm f/2.8 on the Zeiss Batis 18mm f/2.8 web page shows the software-corrected distortion graph, a practice I heartily dislike in a data sheet. An easily-missed note below that graph reads 'camera correction on' . [the note ought to be part of the graph itself, and in red or such]. One reader has already informed me of my “error” in showing the graph below (supplied by Zeiss of course).
Sony mirrorless cameras apply distortion correction to JPEG only (and only if enabled), so unless distortion correction is performed during RAW conversion, the results are as shown below in the Uncorrected graph. Since no ACR lens profiles yet exist for the Batis 18/2.8, all my review coverage of the Batis 18/2.8 is without distortion correction—exactly what the lens actually images.
Distortion correction has implications for sharpness and micro contrast, and thus a true optical distortion chart is an essential part of the data sheet. My graphs below are supplied by Zeiss. Toggle to compare optical distortion to software-corrected distortion. Distortion is one competing optical design tradeoff among many, and apparently for the Batis 18/2.8, it is/was a tradeoff necessary to build the highest-performing 18mm lens yet available.