The reader is strongly advised to read the lens evaluation notes.
The Voigtlander Ultron 40mm f/2 SL II is a manual focus but fully electronic (“chipped”) lens, so it acts just like any Nikon-made lens, supporting 1/3 stop apertures and auto aperture control.
The 40/2 is a “pancake” lens for a compact-carry system. It is as small a lens as one can find for a Nikon body. Such a compact lens must necessarily compromise performance (there are only 6 elements after all). Thus, stopping it down to ƒ/5.6 for best quality is not at all unexpected for such a simple design.
The 40/2 has an aperture ring, and thus can also be used on Canon EOS with a mechanical lens adapter. It is small and light and very compact. Build quality is similar to Zeiss lenses.
The Voigtlander Ultron 40mm f/2 SL II offers good sharpness for the central 1/3 of the frame by ƒ/2.8, but for sharpness over the frame, ƒ/5.6 is mandatory, with ƒ/4 acceptable so long as full sharpness at the edges and corners is not required. The sharpness improvement is moderate at wider apertures; the big jump occurs to ƒ/5.6.
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