Lens distortion
Lens distortion is something I often ignore, but for some subjects such as architecture, low distortion outweighs other considerations. Shown below is the view from one of my favorite places (on my back about to take a nap). While not perfectly framed (it was taken handheld), the distortion is evident, and quite inappropriate for this particular image. Yet it’s an amount of distortion not at all unreasonable in a 50mm f/1.4 lens design. (Here the Zeiss ZF 50/2 Makro-Planar would have been a better choice for its lower distortion).
Evident distortion — Zeiss ZF 50/1.4 Planar
Distortion that is more or less linear is easy to correct in software and indeed the ZF 50/1.4 Planar offers that possibility. Zoom lenses and other specialty designs might have a “wave” or “moustache” distortion that is much more problematic.
Evident distortion — Zeiss ZF 50/1.4 Planar
The bottom line is that every lens is optimized to best satisfy a particular set of design constraints. The ever-popular delusion of judging lenses on test-chart sharpness is sure to disappoint when artistic images are to be made, and/or real scenes with widely-varying color and lighting and contrast are photographed. Find out more about the salient differences between lenses in Zeiss ZF Lenses as well as Canon EF 14/2.8L II.