The Unloved and the Unrivalled

Canon 24mm f1.4 L v Zeiss Contax 21mm f2.8 Distagon

Performance at f8 (Zone A)

Canon 24mm f1.4 L at f8 (centre)	Zeiss Contax 21mm f8 (centre)
4.5 points	5 points

Still a step ahead even as the gap narrows at f8 centre frame, the Contax Distagon outresolves the 5D sensor from f4 through to f11.

Performance at f8 (Zone B: Left Side)

Canon 24mm f1.4 L at f8 (mid-frame)	Zeiss Contax 21mm f8 (mid-frame)
4.5 points	5 points

The 21mm f2.8 is untouchable at this aperture, outperforming the Contax N 17-35mm, Nikon 17-35mm, Canon 24mm L et al.

Performance at f8 (Zone C)

Canon 24mm f1.4 L at f8 (extreme corner)	Zeiss Contax 21mm f8 (extreme corner)
4.75 points	5 points

Among lenses wider than 28mm, it's rare that the corners of the frame are really rendered with this degree of excellence at f8; most require another stop at least to get close. You may also have noticed that the Distagon is practically aberration-free with regard to chroma.