Ross Teleros 4-inch 101.6mm f/5.5 (Collapsible)

Ross Teleros 4-inch 101.6mm f/5.5 (Collapsible)

The Ross Teleros 4-inch f/5.5 is an early British telephoto made in Leica screw mount. Its collapsible black-and-nickel barrel and uncoupled focusing arrangement reflect a period when independent manufacturers were expanding the limited lens choice available to early Leica users.

Optical Qualities

The 4-inch focal length corresponds to approximately 101.6mm on 35mm film, producing a short-telephoto field of view suitable for portraits and distant details. Reliable surviving documentation does not establish the exact optical grouping or diaphragm specification, so those fields are intentionally left open. Performance depends heavily on the optical condition and calibration of each surviving example.

History

Ross supplied interchangeable telephoto lenses for Leica cameras before Leitz offered a broad range of standardized alternatives. Period and collector research places the 4-inch f/5.5 Teleros in the early 1930s, while auction documentation identifies an original collapsible M39 example from that decade. These lenses are now uncommon collector pieces.

Handling

The lens retracts to reduce its stored length and extends for photography. Focusing is by distance scale because the original Leica screw-mount version is not mechanically coupled to the camera rangefinder. A separate finder with an approximately 100mm field of view is recommended for framing.

Compatibility

The documented version uses the Leica M39 screw mount, commonly called LTM. It can be attached to compatible screw-mount cameras and to Leica M bodies with an adapter, but focus must be established by scale, ground glass, live view or another through-the-lens method. The rangefinder does not provide coupled focus confirmation.

Sources

• Leitz Photographica Auction, Ross Teleros 5.5/4-inch black and nickel
• The Leica Society, Interchangeable British lenses on Leicas