The 14-24 is fairly sharp wide open, but low in contrast. It improves noticeably at f/4, then delivers a solid image at f/5.6.
The 16-35 can’t match the 14-24 at f/4, but comes very close at f/5.6, and matches it at f/8.
The 17-35 requires f/8 for a solid image, remaining soft through f/5.6.
The 20/3.5 improves marginally from f/4 through f/11.
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