The widest of the Voigtlander for Canon mount lenses, the 20mm Skopar is a manual focus lens that has electronics to allow the camera to set auto exposure and white balance.
This is an amazingly small but very sharp lens that’s reasonable competition to the Zeiss ZE 18mm f/3.5 and Zeiss ZE 21mm f/2.8 lenses from a sharpness standpoint. It’s reasonably priced, too, and comes in a very small package that makes a great walkaround.