DK-Optic Impastolite 2-inch 51mm f/1.5 M

DK-Optic Impastolite 2-inch 51mm f/1.5 M

The DK-Optic Impastolite 2-inch 51mm f/1.5 M is a modern, rangefinder-coupled Leica M lens inspired by the rare Dallmeyer Septac Anastigmat 2-inch f/1.5. Announced in 2025, it combines a historically styled fast normal-lens formula with a newly manufactured Leica M barrel. Its unusual 51mm focal length reflects the two-inch designation associated with the original British lens rather than the rounded 50mm description used in early coverage.

The Impastolite employs seven elements in five groups and covers the full 24 × 36mm frame. It focuses to 0.7 metres with rangefinder coupling and uses an 18-blade diaphragm. Aperture control is provided through a dampened manual preset mechanism covering f/1.5 to f/11. The exterior barrel is made from 7075 aluminium, while the focusing helicoid and aperture components are machined from brass. At 179 grams without caps, it is relatively light for a fast 51mm Leica M lens.

Two optical versions are offered in black barrels. One uses a vintage-style amber coating, while the other is uncoated. Both versions share the same documented optical formula, mechanical dimensions and Leica M mount. The lens accepts 43mm filters directly on the barrel, while the supplied threaded hood has a 46mm filter thread. DK-Optic states that new-old-stock optical glass is used, although the glass types, manufacturing dates and source have not been independently documented.

Optical qualities

Rendering

The Impastolite is designed to preserve visible residual aberrations rather than reproduce the highly corrected rendering of a modern 50mm lens. Independent testing describes glow, reduced wide-open contrast, pronounced subject separation and a gradual transition into defocused areas at f/1.5. Contrast and definition increase as the lens is stopped down, with more controlled results reported between approximately f/2.8 and f/4.

Sharpness

At maximum aperture, the lens prioritises atmospheric rendering over uniform sharpness across the frame. Fine detail and contrast improve noticeably when stopped down. Published independent testing does not include laboratory MTF measurements, so exact centre and corner resolution figures are unavailable.

Bokeh and transitions

The 18-blade diaphragm helps maintain rounded aperture geometry when the lens is stopped down. Depending on focusing distance and background structure, the lens can produce swirling peripheral blur, softened highlights and gradual transitions between focused and defocused areas. Busy backgrounds may appear more pronounced than with highly corrected modern lenses.

Flare resistance

Strong backlighting can produce halation, reduced contrast and layered flare patterns. These effects are more likely to be prominent with the uncoated version. The amber-coated version is intended to moderate flare, although it should not be expected to perform like a modern multicoated lens. A detachable metal hood is included.

Digital use

The native Leica M mount permits direct use on Leica M film and digital cameras. Accurate rangefinder calibration is important at f/1.5, particularly near the 0.7-metre minimum focusing distance. The smooth, clickless preset aperture may also be useful for video, but photographers accustomed to click stops may need to verify the aperture position visually.

History

Development and Launch

DK-Optic announced the Impastolite in November 2025 as a Leica M adaptation of the optical concept associated with the Dallmeyer Septac Anastigmat. Early announcements generally called it a 50mm f/1.5, while the production lens is officially identified as a two-inch, 51mm model. The original Septac was a rare British high-speed lens used for photographic and cinematographic applications, with surviving examples attracting substantial collector interest.

The historical Septac is commonly described as a seven-element design, although published accounts differ regarding its exact grouping. The production Impastolite is officially specified as seven elements in five groups. It should therefore be catalogued using DK-Optic’s confirmed production specification rather than specifications attributed to individual original Septac versions.

Production Evolution

No major revisions to the Impastolite have been documented since its introduction. Early publicity mentioned black and silver finishes, but the current manufacturer listing identifies two black versions differentiated by their optical coating. No confirmed production total, serial-number allocation or discontinuation date has been published.

Special Editions/Variants

Two factory variants are currently documented: Black with Amber Coating and Black Uncoated. They appear to share the same dimensions, weight, optical configuration, aperture mechanism and rangefinder-coupled Leica M mount. No numbered commemorative or dealer-exclusive editions have been confirmed.

Collector Notes

Collectors should verify the coating version, serial number and originality of the black finish. The amber-coated optics should show a visible coating colour, while the uncoated version may display stronger reflections and flare. Buyers should inspect rangefinder calibration at close distances, focusing smoothness, preset-aperture operation, optical haze and the condition of the numerous aperture blades.

Original accessories include a machined metal front cap, detachable metal hood and DK-Optic presentation box. The difference between the 43mm barrel thread and 46mm hood thread should be considered when purchasing filters. The modern Impastolite should not be represented as an original Dallmeyer lens or a factory Dallmeyer conversion.

Sources

• DK-Optic. Impastolite 2-inch 51mm f/1.5 M.
• Keith Wee Photography. DK-Optic Impastolite 2-inch 51mm f/1.5 Review, The Dallmeyer Septac Glow for Dreamers.
• Leica Rumors. New DK-Optic Impastolite 50mm f/1.5 Lens for Leica M-Mount.
• Leitz Photographica Auction. Dallmeyer Septac Anastigmat 1.5/51mm.