Sharpest f1.4 of f1.8 50mm (approx) Prime Lens.

Dear All,

I am looking for a Nikon Lens or any third party approx. 50mm prime lens which produces the sharpest photo from center to corners when full open. Kindly suggest Lenses which are currently in production because I want to buy it new.

All lenses I have seen so far produces sharp images only when stopped down.

Thanks.

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D.Mukherjee