Leica Summaron 35mm f/2.8 SIMOO

Leica Summaron 35mm f/2.8 SIMOO

The factory code SIMOO identifies the screw-mount (LTM / M39) variant of Leica's Summaron 35mm f/2.8, distinct from the bayonet versions made for the M2 (SIMOM) and the goggled M3 (SIMWO) [1]. All three carry the same optical block, so the difference between them is the mount and the rangefinder coupling rather than the glass [1]. This thread-mount edition was intended for the older Barnack-style screw cameras, where a 35mm focal length sits at the wide end of the system and is typically used with an accessory 35mm finder such as the SBLOO [1][3]. Among Leica's classic wides it has long appealed to collectors and users as one of the most affordable ways into Leica 35mm glass [2][3].

The optical design is a six-element, four-group arrangement, a near-symmetrical double-Gauss type that is single coated, and the diaphragm uses ten blades stopping down to f/22 in full-stop clicks [1]. The barrel is built largely from chromed brass with a metal focus tab, and the focusing action and aperture ring are noted by users for their smoothness and precision [1][2]. It takes the standard 39mm Leica filter thread, and the front element does not rotate during focusing [1]. As a screw-mount lens its closest focus is one meter, longer than the bayonet versions, which focus nearer because they were calibrated for the M cameras [1]. The barrel also includes an infinity-focus lock released by pressing the focus tab, a handling feature shared with the M-mount versions [1].

The Summaron 35mm f/2.8 was made from 1958 to 1974 and sold alongside the faster, more expensive Summicron 35mm f/2 introduced the same year and the Summilux 35mm f/1.4 that followed in the early 1960s [1][2]. Leica positioned it as the more economical standard wide angle for general black-and-white and color work where maximum speed was not required [2]. The screw-mount SIMOO version carried the later catalogue number 11006 [1].

Optical qualities

Rendering The lens is generally described by users as sharp at the center from wide open, with vintage-leaning color and contrast typical of single-coated 1950s Leica glass [1][2]. Performance is reasonably consistent across the frame once stopped down, and reviewers regard f/5.6 to f/8 as the optimum range for even sharpness [1].

Distortion and vignetting Distortion is very low, effectively invisible in normal use [1]. Light falloff in the corners is minor to moderate wide open at f/2.8, reduces by f/4, and is essentially gone by f/5.6 [1].

Flare resistance The simple six-element formula is fairly resistant to flare and ghosting, though as a single-coated design it is less flare-resistant than later multicoated lenses [1].

Collector and user notes Opinions on edge and corner performance vary by sample and use. Some users find their copies softer at the edges at wider apertures or note field curvature, while others report strong across-the-frame results once stopped down, so individual condition and expectations matter [2].

History

Development and Launch The year 1958 was the first time Leica owners could choose among several 35mm lenses, as the Summaron 35mm f/2.8 and the Summicron 35mm f/2 both arrived together [2]. The earlier 3.5cm f/3.5 Summaron, itself a six-element design that had replaced the 1930s 3.5cm Elmar, was the screw-mount predecessor to this faster f/2.8 lens [1][2]. With the Summilux 35mm f/1.4 added soon after, Leica offered a full 35mm range from f/1.4 to f/2.8 that lasted until the Summaron was discontinued in 1974 [2].

Production Evolution Across its run the lens was offered in three mount and finder configurations sharing the same optics: a screw-mount version (SIMOO), an M-bayonet version for the M2 (SIMOM), and a goggled M-bayonet version for the M3 (SIMWO) whose auxiliary finder optics fit the 35mm field into the M3's 50mm finder [1]. The factory five-letter codes were later replaced by numeric catalogue numbers, with the screw-mount lens becoming 11006 [1].

Special editions No widely documented factory special editions are specific to the screw-mount SIMOO; the principal variations are the mount and finder differences between the screw, M2, and goggled M3 versions [1].

Collector Notes The SIMOO is distinguished from its siblings by its M39 thread mount and one-meter minimum focus, and it lacks the goggles found on the M3 version [1]. Buyers should check the single-coated glass for haze, cleaning marks, and separation, and confirm the smooth focus and infinity lock operate correctly [1][2]. Period accessories worth verifying include the correct screw-mount finder (SBLOO), 39mm front and rear caps, leather case, and the appropriate hood; later rectangular Leica hoods from modern 35mm lenses are reported to fit the same front diameter [1]. Some reviewers caution that prices for the f/2.8 Summaron can run high for a slow lens, with the older f/3.5 Summaron usually selling for less [1][2].

Sources

• [1] Ken Rockwell. Leica Leitz 35mm f/2.8 Summaron (1958-1974). https://www.kenrockwell.com/leica/35mm-f28.htm
• [2] f8low. A closer look at the Summaron 35mm 2.8 on film. https://www.f8low.com/a-closer-look/summaron-35mm-f2.8
• [3] Dan Kerin Photography. Leica 35mm f/2.8 Summaron. https://dankerinphotography.com/leica-35mm-f28-summaron