Voigtländer Ultron 35mm f/1.7 II

Voigtländer Ultron 35mm f/1.7 II

Cosina built the Ultron 35mm f/1.7 II as a thoroughly redrawn successor to the original screw-mount Ultron 35mm f/1.7 Aspherical of 1999, this time optimised for use on digital rangefinder sensors rather than carried over unchanged. It was announced in late 2014 and reached the market in 2015 as a Leica M-mount lens, sitting below the faster f/1.2 and f/1.4 Noktons in the company's 35mm line while offering a markedly higher level of corner sharpness wide open [1][2]. The combination of a fast f/1.7 aperture in a notably small and light barrel is the trait that has earned it a following among M shooters and adapter users alike.

Optically the lens uses nine elements in seven groups, including one aspherical surface, and stops down through a ten-blade diaphragm that keeps out-of-focus highlights round well past maximum aperture. The aperture ring clicks in half stops from f/1.7 to f/16, while the focusing ring is unusually thin and, by several accounts, less comfortable to grip quickly than the aperture collar. Build is all metal and glass with engraved, paint-filled markings, the mount is rangefinder coupled, and minimum focus is 0.5 m, which is conventional for an M lens but limiting for close work unless a helicoid adapter is used. The lens takes 46 mm filters and ships with a screw-in hood noticeably wider than the barrel, plus a second cap that fits over the hood.

The II was offered in two finishes that share the same optics: a lighter black version with an aluminium barrel and a heavier silver version with a brass focusing ring, the latter priced higher. Distinguishing the newer design from the earlier 1999 screw-mount Ultron is straightforward, since the two are entirely different optical formulas; the M-mount black version carries no red markings on the focus ring, the silver version shows a dark band at the centre of the barrel, and both newer barrels are slimmer at the middle. The earlier M39 lens is engraved Aspherical and uses a different focusing ring, and reports consistently rate it below the M-mount II for both sharpness and contrast at f/1.7.

Optical qualities

Rendering The Ultron 35mm f/1.7 II is documented as a high-contrast, very sharp lens with smooth, well-behaved out-of-focus rendering, an unusual balance for a fast and compact 35mm design. Its behaviour depends heavily on the camera it is mounted to, performing best on the thin filter stack of Leica bodies and showing more compromise on thicker-stack mirrorless sensors.

Sharpness Reviewers describe it as sharp across most of the frame from f/1.7, excellent over most of the frame by f/2.8, and very sharp across the field at f/8 when focus is placed to account for its field curvature.

Bokeh and transitions The bokeh is regarded as smooth at shorter distances, with round highlights helped by the ten-blade aperture and a pronounced cat's-eye shape toward the edges wide open; at longer distances the rendering becomes more nervous, particularly in the corners.

Flare resistance Flare control is rated very highly, with ghosting hard to provoke and well-defined sun stars appearing from around f/2.

Distortion and vignetting Barrel distortion is described as negligible. Vignetting is heavy wide open and remains visible stopped down, an effect amplified on mirrorless sensors and far less of an issue on Leica bodies.

Aberrations Lateral chromatic aberration is well corrected and hardly visible, and longitudinal CA, while present, is reported as well controlled.

Digital use On the Leica M240 the field is reported to be relatively flat, whereas on Sony A7-series bodies the thick filter stack induces pronounced field curvature and stronger corner color shift, with the effect easing on later, less reflective sensors.

History

Development and Launch The lens replaced the first Cosina Voigtländer 35mm f/1.7, an aspherical screw-mount design dating to 1999, and was reworked specifically to perform better on digital sensors. It was announced in late 2014 and went on sale in 2015 in Leica M mount. Around the same period Cosina began moving parts of its rangefinder catalogue toward native Sony E-mount versions with electronic contacts, but the Ultron 35mm f/1.7 II itself is a coupled M-mount lens without electronic data transfer.

Special editions No major factory special editions of this lens are widely documented; the principal variation is the choice of black aluminium or silver brass finish.

Collector Notes The most common point of confusion is between this M-mount II and the older M39 Ultron 35mm f/1.7 Aspherical, which look broadly similar but are optically unrelated and command different prices; the older lens is engraved Aspherical and is reported to be less sharp and lower in contrast wide open. When buying, verify the finish against the weight expected, since the silver brass version is heavier than the black aluminium one, and confirm the infinity hard stop behaves correctly, as adapter and sample tolerances can leave infinity reached early on mirrorless bodies. Worth checking are the original screw-in hood and its two caps, which are easily separated from the lens over time.