MS-Optics Sonnetar 50mm f/1.3 Slim

MS-Optics Sonnetar 50mm f/1.3 Slim

Built by Miyazaki Sadayasu, the one-man workshop behind MS-Optics, the Sonnetar 50mm f/1.3 Slim is a fast, unusually compact normal lens for the Leica M mount that arrived in 2022 [1][2]. The Sonnetar name is a deliberate homage to the Zeiss Sonnar, and the lens follows the optical philosophy of that classic design rather than chasing clinical correction [2]. Reviewers framed it as a lighter, slightly slower companion to Miyazaki's earlier 50mm f/1.1 Sonnetar, trading some speed and weight for a more usable maximum aperture [1]. It can also be read as a spiritual successor to the very first MS-Optics product, the MS-Mode 50mm f/1.3 released in 2006 [2].

Optically the lens uses a Sonnar-derived layout of five elements in four groups, with a 14-blade aperture that stops down to f/16 [1][2]. The barrel is all metal and very small for a fast fifty, weighing about 127 g, and it accepts 49 mm filters through a reversed, male thread, with a supplied metal hood that adds a conventional 55 mm thread inside it [1][2]. Handling carries the quirks typical of Miyazaki lenses: a clickless aperture ring that turns roughly 90 degrees and rotates in the opposite direction to most M-mount lenses, plus a unit-focus design in which the whole front barrel, including the aperture ring and front element, rotates while focusing [1][2]. Because of this, the usual practice is to set the aperture first and then focus [1][2]. A small focus lever aids the otherwise short focus throw of about 120 degrees down to a close-focus distance of 0.6 m [2]. A rear adjustment ring is provided for fine calibration, and a coma adjustment is also accessible at the back for users who like to tinker [1][2]. On a Leica M10 the small barrel causes only minimal viewfinder blockage even with the hood fitted [2].

As a hand-made boutique lens produced in small numbers, the Sonnetar 50mm f/1.3 Slim has limited documented variation, and no major factory special editions are widely recorded. Reviewers note that, like other MS-Optics lenses, the six-bit code groove on the rear may not be fully covered, which can confuse the lens detection on some digital M bodies until the groove is taped over [2].

Optical qualities

Rendering The lens delivers the Sonnar-style character its name implies: a degree of glow from undercorrected spherical aberration wide open, giving a soft, slightly dreamy look that clears up by around f/2 [2]. Compared with Miyazaki's other fast fifties, this glow is less pronounced, which makes the lens more usable at maximum aperture [2].

Sharpness Central sharpness and contrast are reasonable at f/1.3 and improve on stopping down, but the corners are weak at wider apertures and the lens shows noticeable field curvature [2]. One reviewer felt the new Sonnetar looked sharper in the center wide open than the older f/1.1 version [1].

Bokeh and transitions The out-of-focus rendering follows the Sonnar pattern, somewhat busy or "funky" at maximum aperture and generally more pleasant a stop or two down [2].

Flare resistance Flare is a known weakness. With the sun outside the frame the lens can produce large, sometimes frame-filling artefacts; stopping down or shading the front element helps considerably, and reviewers often chose f/2 to suppress flare with point lights in the scene [1][2].

Distortion and vignetting Distortion has an unusual profile: most of the frame is essentially distortion-free, but it becomes strongly visible toward the corners, so a lens-specific correction profile is needed for a clean result [2]. One reviewer found the level of distortion higher than typical for a 50 mm lens, an area where the older Sonnetar performed better [1].

Aberrations Coma correction is poor, with point light sources taking on smeared shapes near the corners, consistent with the lens's field curvature [2]. Lateral chromatic aberration is on the medium-to-strong side but corrects well in software, while longitudinal CA and purple fringing are present and partly masked by spherical aberration wide open [2].

Collector and user notes The appeal of this lens lies in its tiny size, vintage casing, and distinctive rendering rather than technical perfection; reviewers describe it as a contrasty, cinematic, classic-Sonnar look that returns to the spirit of earlier Miyazaki designs [1][2].

History

Development and Launch MS-Optics is the brand of Japanese optical designer Miyazaki Sadayasu, who hand-assembles his lenses in small batches [2]. The 50mm f/1.3 Sonnetar Slim was released in 2022 as one of several fast 50mm designs in his catalogue [1][2]. Its lineage connects both to the earlier 50mm f/1.1 Sonnetar, which earned a cult following and sold out quickly, and to the 2006 MS-Mode 50mm f/1.3, the first MS-Optics lens [1][2].

Collector Notes Because these are boutique, hand-built lenses sold in limited quantities, availability is intermittent and prices on the used market have been high relative to their size [2]. Buyers should verify that the supplied round metal hood is present, since it carries an additional 55 mm filter thread, and should remember the reversed 49 mm front thread when fitting filters, as circular polarizers will only work in one orientation [2]. The rear adjustment ring and coma adjustment are normal features of the design rather than signs of damage, but the partially exposed six-bit groove may need taping to avoid lens-detection issues on digital M cameras [1][2]. Note that one published review lists the lens as rangefinder coupled to roughly 0.8 m, a point not reflected in the confirmed specifications recorded here, so coupling behaviour is worth checking on the specific copy before purchase [1].

Sources

• [1] Japan Camera Hunter. Lens review: MS Optics Sonnetar 50mm 1.3 Slim. https://www.japancamerahunter.com/2022/04/lens-review-ms-optics-sonnetar-50mm-1-3-slim/
• [2] Phillip Reeve (BastianK). Review: MS-Optics 50mm 1.3 Sonnetar Slim. https://phillipreeve.net/blog/review-ms-optics-50mm-1-3-sonnetar-slim/