These are some test images I made for my own purposes.  I was specifically looking at central sharpness of the Voigtlander 40mm Nokton 1.4 at various large apertures when mounted on the Nikon Z7.

I took two series of test shots, one at close-ish distance and the other at mid-far distance.

As you can see, @ f/1.4 there is a definite softness and “glow”, but resolution is actually quite good.  By f/2, the lens takes on a more modern contrasty look, which improves @ f/2.5, and then very slightly again @ f/2.8.

Depending on the look I’d want, I could see myself shooting at each of these apertures, but for a general-purpose look f/2 is probably the best compromise; @ f/2.5, the sharpness is already beyond anything I’d need for portraiture.

—Peter.

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Scene 1:

(focus is on the number “30”)

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Scene 2:

(focus is on the word “LIFETIME”)

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As “dreamy” as the shots @ f/1.4 appear, they can easily be made to approximate the ones @ f/2, if contrast and sharpness are added during post processing:

(as stated in the introduction, the resolution is all there)

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Transforming the “LIFETIME” image @ f/1.4 to a more modern rendering is a little more tricky, because there is more “glow” present, but — again — adding contrast and sharpness helps.

BY THE WAY, the Voigtlander 40/1.4 Nokton I have is the single-coated (SC) version.  The multi-coated (MC) version may behave differently, as it is purported to render with more contrast, have less propensity to flare, etc.  However, having owned it in the past I can’t recall seeing a difference, though admittedly I’ve never done a side-by-side comparison.

I hope you found this useful.

—Peter.