The bottom line for wide aperture shooting: understand your lens, and realize that it’s the overall visual impact that matters, not absolute sharpness. If you’re after peak sharpness, shoot at f/8.
Even the very best fast lenses have considerable aberrations wide open, which makes focus somewhat ambiguous, particularly off-center (though spherical aberration affects the entire frame). Therefore, the expectations for crisp and contrasty results must be reduced. This is true even for the US$10,500 Leica Noctilux-M ASPH, which has a truly exotic optical design, with numerous special elements (correcting an f/0.95 lens is far more stringent than for an f/1.4 lens).
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