Omnar Bertele 5cm f/2 MC FLB
The Omnar Bertele 5cm f/2 MC FLB is a modern recreation of the classic 5cm f/2 Jena 6 elements in 3 groups lens formula from 1934 by Dr. Ludwig Bertele.
Unique to the Bertele is the introduction of the Floating Lens Block (FLB) system by Omnar Lenses
Price (Starting from):
£2750.00 (excl. VAT)
Features & Specifications
Optical Formula:
6 Elements in 3 Groups, Floating Lens Block Assisted
Lens mount:
M-Mount
Size & Weight:
35mm (protrusion off camera)
260 grams
Filter size:
E39
Coatings:
Multi-Coated – Sapphire Blue and Amethyst Violet
RF coupled:
0.7m – Infinity
Construction:
All brass helicoid
Made in the UK:
Designed, manufactured, hand finished and hand-assembled in the UK
The Omnar Bertele 5cm f/2 MC FLB (‘Bertele lens’ for short), is a modern recreation of the classic 5cm f/2 Jena 6 elements in 3 groups lens formula from 1934 by Dr. Ludwig Bertele. It is a culmination of over 5 years of ongoing research, development, design and engineering by Skyllaney Opto-Mechanics. This 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.
Background
The classic versions of this lens formula from the 1930s through to the 1940s are wonderful lenses. Here at Omnar Lenses we have long been fanatical about their optical rendering – in fact it is through being fans of this formula that Omnar’s founders Chris and Hamish originally bonded back in 2020. But, as anyone who knows the formula well will tell you, these classic lenses are not without their issues. These issues include the use of soft type optical glass, scarcity of quality and undamaged coatings, limitations of the lens mounts they are available in – and most well documented – the issues of focus shift that makes them almost unusable for perfectly accurate focus at middle apertures and close shooting distances.
The Bertele – Modern Glass
The early versions of lenses using this formula utilised a soft type of optical glass which was very easy to scratch. Thus, many vintage copies of the formula have heavy cleaning marks and scratches on front and rear element surfaces. The classic versions also came in three different coating types; uncoated, single coated and multi-coated.
The multi-coated versions were the most rare, and very few mint specimens exist due to the usage of soft glass and them now being over 80 years old. The optical glass type used in this era also pre-dates the invention of ultrasonic curing, and thus many glass elements of the vintage specimens have internal air bubbles. Also very few native LTM versions were made, so there are even less that can now be readily mounted to Leica cameras.
The Bertele lens addresses the susceptibility of optical wear that the vintage versions had by implementing modern scratch resistant glass which has been ultrasonically cured to ensure air-bubble free elements. The signature blue and violet multi-coating found on the late war era versions, have also been replicated on the Bertele lens.
The Bertele – FLB system
Unique to the Bertele lens is the introduction of the Floating Lens Block (FLB) system by Omnar Lenses (read more about FLB below). 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 is able to achieve the same qualities of the bokeh as the classic Jena version.
The Bertele – Reverse slope RF cam / m-mount advantage
Historically, the 1930s Jena versions of this formula, along with its later derivatives made by other manufacturers into the 1950s, had a secondary focus shift also that most users would not be aware of because it only appeared below 1 meter focus distance. This secondary shift occurred as a result of the outer element aberrations entering into a continually heightened state the closer the lens was made to focus, triggering a run-away EFL recompilation (this is also the reason why many fast rangefinder lenses that are f/1.2 and f/0.95 in aperture value wide open are limited in their close focus abilities). The classic versions of the Jena lens formula in LTM mount were often limited to 1-meter minimum focus distance (MFD), as the linear translation RF cams on those lenses could not cope with the sub 1m EFL recompilation. This 1m MFD limit would be continued by other manufacturer’s post war until lens formulas of this type were gradually discontinued in the late 1950s due to the more mainstream arrival of the double gauss lens formula on rangefinder cameras.
The Bertele lens addresses this secondary close focus limitation of these formulas by implementing a pre-loaded reverse sloped RF cam that is non-linear. The RF cam of the Bertele lens is not only able to translate the 52.4mm EFL value of the lens formula down to the 51.6mm EFL calibration that modern M mount rangefinder cameras use, but is able to deviate into non-linear territory in this sub 1-meter focus distance to continue to track the varying EFL that is being induced exponentially the closer and closer this classic lens formula is made to focus. This is possible by utilising the m lens mount – it would not be possible to achieve with an LTM mount lens.
The Bertele – A symphony of advancements
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.
All this is achieved not by modifying the original lens formula in any meaningful way in order to retain the character and sanctity of how they rendered originally, but by the complex orchestration of brass mechanical parts inside the Bertele lens that move the rear optical carriage of the optical block depending on the aperture value set, and the RF cam accurately positioning itself non-linearly to match the varying EFL value the formula exhibits from the 0.7m through Infinity focal ranges.
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. 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 Bertele – Digital Medium Format Compatible
The Bertele lens has also been designed to provide full sensor coverage on digital medium format sensors (44mm × 33mm), as found on the Hasselblad XCD and Fuji GFX camera series.
The Bertele lens provides vignette-free usage on these cameras and becomes a 42mm full-frame equivalent focal length lens, thanks in part to its generous 62mm image circle. The image circle on the Bertele lens is larger than that found on the classic 5cm f/1.5 Jena formulas, further aiding its peripheral illumination performance on both full-frame and digital medium format sensors.
Available for download here is an image of the beautiful seaside town of Helensburgh, Scotland. This image was shot using the Bertele lens at f/11 on a Hasselblad X1D camera.
Pre-Order your Bertele
Below you will find three options for preordering your Bertele lens. The first option is to order against the first production batch which will be delivered September 2025. If ordering from this first batch you have the option to either place a deposit, or pay the full price up front. If you pay a deposit, we will be in touch in September with a payment link for the final payment.
Because the numbers for this first batch are limited, we are also making it possible to pre-order at a lower price against batch two and batch three. Again, when these lenses are ready to ship, we will be in touch to take the final payment.
Please note: the total price of the lens is the same regardless of the batch, we are simply offering a lower deposit on future batches as delivery will be further into the future.
Pre-Order Batch One
The first limited production run of this lens will comprise a total of 30 lenses. We anticipate all lenses will be ready to ship by the end of September 2025.
Please note: The first batch pre-order has now sold out, if you would like a Bertele lens, please pre-order against batch 2 or 3 below.
Matte Black: £2750
Silver Matte, Satin Black, Black with Brass: £3000
Engraving: £50 extra
VAT is calculated in addition to these prices for UK customers only and will be added in the cart.
£1,000.00 – £3,050.00 Price Excl. VAT
Pre-Order Batch Two
The second limited production run of this lens will comprise a total of 50 lenses. We anticipate all lenses will be ready to ship February-March 2026.
Matte Black – £2750
Silver Matte, Satin Black, Black with Brass – £3000
Engraving – £50 extra
VAT is calculated in addition to these prices for UK customers only and will be added in the cart.
This is a deposit against the final total price.
£750.00 Price Excl. VAT
Pre-Order Batch Three
The third limited production run of this lens will comprise a total of 50 lenses. We anticipate all lenses will be ready to ship May-June 2026.
Matte Black: £2750
Silver Matte, Satin Black, Black with Brass: £3000
Engraving: £50 extra
VAT is calculated in addition to these prices for UK customers only and will be added in the cart.
This is a deposit against the final total price.
£500.00 Price Excl. VAT
The open source FLB system
They say if you love something, you must give it away. We believe the FLB system inside the Bertele lens is one of the biggest advancements to rangefinder lens design since the implementation of ASPH and FLE lenses, as it has the potential to resolve all other focus shift phenomenons on past and present lens formulas. Omnar lenses has always been passionate about rangefinder lenses, especially the vintage formulas from yesteryear, our Bertele FLB lens is a tribute to just one of these classics.
We would love to see other classics remade using the advancements that the FLB technology has to offer. That desire to see what is now possible, and put focus shift finally to rest, is why we are releasing the schematics and design of how the FLB system works so that other lens designers and manufactures can implement it as they see fit. Our goal has been to resolve EFL recompilation issues affecting focus shift once and for all, and we believe FLB is that solution.