Omnar Lenses has announced the Omnar Bertele 5cm f/2 MC FLB. The 50mm f/2 prime lens is a modern recreation of the classic 5cm f/2 Jena lens created in 1934 by Dr. Ludwig Bertele. Omnar has spent the last five years researching, developing, designing, and engineering its latest lens.
Omnar Lenses is a joint effort by Hamish Gill, known for the photography website 35mmc.com, and Chris Andreyo of Skyllaney Opto-Mechanics, a company known for repairing and building unusual custom lenses for Leica M-mount. Gill and Andreyo are both passionate about rangefinder lenses, and their love for them is on clear display with the Omnar Bertele 50mm f/2 lens.
Their effort has “not only been in a bid to bring to market a modern version of this classic lens formula for Omnar Lenses, but in doing so, also resolve all of the significant shortcomings of the earlier versions, whilst retaining the original formula, and therefore the best of the characteristic optical traits.”
The original lenses made in the 1930s and 40s are beloved for their distinct optical rendering. Their shared love of the rendering is actually how Gill and Andreyo first met in 2020. However, they both know that the original formula has issues for modern photographers. The lenses utilize soft-type optical glass, easily damaged coatings, and, most frustratingly, focus shift issues, all of which make it very difficult to find good-quality lenses today, nearly a century later. Even ones in good condition have focus difficulties.
While Omnar is focused on recreating the original Bertele lens as much as possible, they have made some clever modernizations. Instead of using old, soft glass that predated the invention of ultrasonic curing and was therefore prone to air bubbles, the Omnar Bertele lens utilizes modern, scratch-resistant glass that has been ultrasonically cured to eliminate any air bubbles. However, the signature blue and violet multi-coating of the late versions of the Bertele has been preserved.
As for the focus shift issues, the duo has solved that, too. Unique to the lens is a new Floating Lens Block (FLB) system designed by Omnar Lenses. It is a complicated problem to explain and solve, so Omnar Lenses will handle it:
Unique to the Bertele lens is the introduction of the Floating Lens Block (FLB) system by Omnar Lenses (read more about FLB in the additional information section at the bottom). The original 5cm f/2 and f/1.5 versions of Dr. Bertele’s 1930s Jena formulas, suffered from focus shift in the mid aperture ranges. This had to do with the aperture blades suppressing the outer element aberrations upon contraction, which would trigger an effective focal length recompilation. Changes to the effective focal length (known as EFL) are the primary source for the aperture dependent focus shift at the mid zones (f/3.5 through f/6) on the classic versions of these formulas. The post war Oberkochen designed variants of these lenses began to utilize a ninja-star shaped aperture blade system, which would permit some of the outer element aberrations from being fully suppressed as the iris was closed down, thus resulting in a reduced effective focal length recompilation effect. As such, a slight focus shift reduction was present on the Oberkochen variants when compared to the circular bladed versions of the Jena variant. The downside of the usage of the ninja-star shaped aperture blade assembly on the later Oberkochen variants was that it also yielded a poorer quality out of focus rendering (known as bokeh), which often manifested itself as crown-cork shaped out of focus highlights and an overall more nervous looking bokeh.
The Bertele lens is unique in that for the first time, the FLB system inside the lens is able to counteract the optical formulas EFL recompilation, thereby mitigating the focal plane from drifting outside the depth of field (DoF), which ensures that where the rangefinder RF patch is focusing, the lenses focal plane thus remains there from the entire f/2 through f/22 aperture value swing. The FLB system works significantly well enough that a ninja-star aperture blade assembly was not necessary to provide any further EFL recompilation reductions, and as a direct result, the Bertele lens can achieve the same qualities of the bokeh as the classic Jena version.
This is such a big engineering accomplishment — Omnar Lenses calls it one of the significant advancements in rangefinder lens design since the introduction of aspherical and floating lens element designs — that the company is giving the technology away. The FLB System is open source, and lens designers can learn more about it here.
As for the Omnar Bertele 5cm f/2 MC FLB, it also addresses an issue with the original lens and its focus shift at close-focusing distances. The original lens has not just one focus shift problem but a second one that occurs at focusing distances below one meter. To resolve the issue, the Omnar Bertele has a pre-loaded reverse sloped RF cam that is non-linear, meaning that the lens can translate the 52.4mm effective focal length value of the lens formula to the 51.6mm EFL calibration modern M-mount cameras use.
“Thus, for the first time in the over 90 year history of this lens formula, the closer focus distance of this formula can be unlocked with accurate rangefinder usage, and its mid aperture focus shift mitigated to achieve focal plane stability across apertures,” Omnar Lenses explains.
The duo achieved these engineering feats without modifying the original lens formula itself “in any meaningful way.” It remains a six-element, three-group design that promises the character and rendering of the original lens. Essentially, Gill and Andreyo have applied expert modern engineering know-how and manufacturing techniques to the original lens design.
“The end result of this is brand new optics made using modern techniques combined with a symphony of interlocking components that permits the lens formula to accurately focus and maintain its focal plane in sync with the camera’s rangefinder patch across the entire rangefinder coupled focus distance and at all aperture values,” Omnar Lenses says. “No other version of this formula has ever been able to achieve this. In testing this lens, the focus shift has been reduced so much that the Bertele FLB lens is easily exceeding most double gauss lens formulas focal plane to aperture value stability ratings, and this is thanks to the implementation of Omnar’s FLB system.”
The Omnar Bertele 50mm lens also covers medium-format image sensors, including the 44 by 33-millimeter ones found in Fujifilm GFX and Hasselblad XCD series cameras. The lens features a large 62mm image circle, allowing it to cover even some large-format cinema cameras.
Sample Images
Pricing and Availability
The Omnar Bertele 5cm f/2 MC FLB lens is available to preorder now for £2,750, or around $3,717 at current exchange rates. The first production run will comprise just 30 lenses, and Omnar Lenses says they will be ready to ship by the end of September.
Image credits: Omnar Lenses
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