Tokyo Kogaku C Simlar 50mm f/3.5 (Collapsible)

Tokyo Kogaku C Simlar 50mm f/3.5 (Collapsible)

The C Simlar 50mm f/3.5 is a coated, collapsible standard lens made by Tokyo Optical for early Leotax rangefinder cameras. Specialist Leotax research places it mainly with the Special D II, Special D III and NR III period of the late 1940s. The letter C denotes coating and identifies a production stage between early unprefixed Simlar lenses and the updated unprefixed version used from around 1951.

The optical construction is commonly reported as four elements in three groups. The cited Leotax chronology presents the four-in-three attribution through specialist collector research rather than a reproduced Tokyo Optical diagram, so it is preferable to record the numerical formula without assigning an unconditional named design derivation.

The lens has a chrome collapsible barrel, manual aperture control and coupled Leica thread mount focusing. Early examples use the older aperture scale ending at f/18 and are marked 50mm. Minimum focus is approximately 3.5 feet, or 1.07 metres. The front accessory system is A36 clamp-on, not an ordinary 36mm screw thread.

Optical qualities

Rendering

Dependable measured performance information for the exact C Simlar generation is limited. A modern collector review found a Simlar sample broadly competitive with a contemporary Elmar, but that is sample-based evidence and does not establish a universal rendering signature for every C-marked lens.

Sharpness

No controlled test cited here establishes an exact centre-to-corner sharpness profile through the aperture range. The reported four-element, three-group construction does not by itself prove that the lens behaves identically to an Elmar or another collapsible four-in-three standard.

Contrast and flare resistance

The C prefix documents the introduction of coating. This historical feature should not be converted into a promise of modern contrast or flare resistance. Surface wear, internal haze and cleaning marks can outweigh the original treatment, and specialist user evidence notes that fine coating scratches are encountered on surviving Simlar lenses.

Digital use

The lens can be adapted to a mirrorless camera with a suitable LTM adapter. Extend and lock the barrel before making an exposure. Rear clearance must be confirmed before collapsing it into any adapted digital body, because the internal geometry of cameras and adapters differs.

History

Development and Launch

The Leotax Special D II and D III appeared in 1947. Specialist chronology identifies the Simlar and C Simlar 50mm f/3.5 as typical Tokyo Optical lenses for these bodies. The C version became the more commonly documented lens on later Special D III examples and also appears with the small NR III production around 1949.

Production Evolution

The State, early Simlar and C Simlar versions use the older aperture sequence ending at f/18 and carry a 50mm focal-length engraving. The C marks the coated stage.

Around the introduction of the Leotax D IV in 1951, the C prefix was dropped. The later unprefixed Simlar adopted a modern aperture scale ending at f/16 and generally changed the focal-length marking from 50mm to 5cm. These engraving and scale changes are important chronological identifiers, but the available evidence does not demonstrate a new optical formula.

Special Editions/Variants

No separate factory special edition of the C Simlar has been reliably documented. Camera combinations, export markings or accessory sets provide historical context but do not create distinct optical editions.

Collector Notes

Useful identifiers are the C Simlar name, 50mm engraving, f/18 minimum aperture, collapsible chrome barrel and native Leica-thread rear construction. A lens fitted to a period Leotax is contextual evidence, but does not by itself prove an original factory pairing.

Check that the barrel extends fully and locks securely, the rangefinder cam moves correctly and the aperture remains dry. Inspect the front surface under angled light for cleaning marks and coating wear. Use genuine A36 accessories or a suitable clamp-on adapter rather than forcing a threaded filter onto the front.