Voigtländer Ultron 28mm f/1.9

Voigtländer Ultron 28mm f/1.9

When Cosina launched this lens under the revived Voigtländer name, it was the fastest production 28mm lens made for any rangefinder mount, a distinction it held until Leica introduced the 28mm f/1.4 Summilux in 2014 [1]. The odd f/1.9 maximum aperture is the giveaway of that ambition: the practical difference from f/2 is negligible, and the figure reads more like a marketing claim to secure the speed record than a meaningful optical gain [2]. For Leica thread mount users it remains the fastest 28mm available in that mount, which is the main reason collectors and film photographers still seek it out [2].

Optically the Ultron uses 9 elements in 7 groups, including an aspherical element, with a 10-bladed diaphragm that produces clean sunstars and well-rounded out-of-focus highlights [1][2]. It focuses to 0.7 m, which was the long-standing norm for M-mount glass before live-view cameras encouraged closer designs [2]. The lens is all-metal and well assembled, with a knurled aperture ring carrying half-stop clicks and a smooth, well-damped focus ring of roughly 90 degrees of travel [1][2]. Being an LTM (M39) lens, it couples to the rangefinder and can be used on screw-mount bodies directly or on M-mount and mirrorless cameras through an adapter, though an adapter adds a variable that can affect centering and rangefinder accuracy [2]. The lens is physically large for the wide focal length, so it intrudes into the viewfinder of M bodies with or without its hood, and on cameras without 28mm frame lines an external finder is needed [1][2]. Cosina, which acquired rights to the Voigtländer name in 1999, is one of the few Japanese makers with its own glassworks, and this was among its earlier rangefinder lenses [2].

The Ultron 28mm f/1.9 was produced in both black and silver finishes [1][2]. Although the black version resembles Leica black-paint lenses and shows similar brass-coloured wear with use, the barrel is too light to be brass and is most likely anodized aluminium [2]. This early version uses a screw-in focus lever and a petal-shaped hood retained by a small side screw, details that distinguish it from the later M-mount Ultron 28mm f/2, which adopted a different 10-elements-in-8-groups design, a focus tab, and a circular hood while being slightly smaller and lighter [1]. Original accessories included a felt-lined friction-fit cap and the small screw-in focus lever, both of which are often missing from used examples [1].

Optical qualities

Rendering The Ultron is sharp in the center across its range but shows a soft, glowing spherical-aberration look wide open, clearing up noticeably by f/2.8 [2]. Reviewers describe its overall character as slightly "vintage" compared with Cosina's later 28mm lenses, with lower contrast wide open and out-of-focus areas that can become more structured toward the corners [2].

Sharpness Center sharpness is good from maximum aperture, but corner performance lags and best across-frame results come from stopping well down; one widely cited assessment found the lens optimal around f/4 and a little soft wide open, especially at the edges [1][2]. On digital bodies the corners are weaker than on film, and the thinner sensor stack of a Leica M body gives better edges than a thick-stack mirrorless sensor [2].

Bokeh and transitions At a 28mm focal length subject isolation is limited, but close and wide open the lens can produce pleasant background blur, helped by the rounded openings of its 10-bladed diaphragm [1][2]. Field curvature is visible, so out-of-focus rendering can be uneven across the frame [2].

Flare resistance Flare control is a weak point. Unlike Cosina's later coatings, this earlier lens is prone to flare and contrast loss against strong light, and it can throw colored ghosts even with the hood fitted [1][2].

Distortion and vignetting Distortion is low but non-linear, and a lens-profile correction handles it well [2]. Vignetting is heavy wide open, measured at around 3.4 EV in the corners, and remains noticeable until the lens is stopped down [2].

Aberrations Lateral chromatic aberration is minimal, as expected from a design predating the digital era, but longitudinal color is present, with magenta and green fringing on out-of-focus edges and purple fringing that only fully clears around f/5.6 [2]. Coma is fairly strong at f/1.9 and mostly gone by f/2.8 [2].

History

Development and Launch The lens was part of Cosina's revival of the Voigtländer brand, whose rights it acquired in 1999, and which began producing M39 rangefinder lenses shortly after [2]. It was shown at Photokina 2000 and entered the lineup as the speed leader among 28mm rangefinder lenses [1]. LeicaLensList records the production start as 2001; some sources cite a Photokina 2000 debut, a minor discrepancy in dating rather than in the lens itself [1][2].

Production Evolution The f/1.9 LTM version was eventually replaced by an M-mount Ultron 28mm f/2 that used a new optical formula of 10 elements in 8 groups and was slightly smaller and lighter, with revised handling features [1]. Cosina later continued the Ultron 28mm line with further M-mount redesigns that focus closer and use a smaller filter thread, with each generation reported to improve contrast, resolution and flare resistance while reducing size and weight [2].

Collector Notes Verify that an example still has its original screw-in focus lever and friction-fit cap, as both are frequently lost; the empty lever screw-hole is a common sight on used copies [1]. The petal hood mounts with a side screw and must be oriented correctly to avoid obstructing the frame, and it has to be removed to change filters [1]. Black examples often show brassing from wear, which some buyers value and others do not; this is cosmetic and does not indicate a brass barrel [2]. Buyers adapting the lens to digital M or mirrorless bodies should account for the adapter's effect on centering and rangefinder coupling, and should expect significant viewfinder blockage on M cameras [2].

Sources

• [1] Casual Photophile. Voigtlander Ultron 28mm F/1.9 LTM Lens Review. https://casualphotophile.com/2020/11/09/voigtlander-ultron-28mm-ltm-lens-review/
• [2] phillipreeve.net. Review: Voigtländer 28mm 1.9 Ultron. https://phillipreeve.net/blog/review-voigtlander-28mm-1-9-ultron/