Chris (at Skyllaney Opto-Mechanics) emailed me some interesting information on their soon to be completed Bertele lens. He told me that I could post information from his email to RFF.
“The Bertele lens, is basically a remade pre-war f/2 Sonnar. Optically, the formula is extremely similar, down to the radi of curvature and glass dispersion types. What differs optically, is the slight outer diameter of the elements, to fit inside more modern means of mechanics. The original Zeiss Jena f/2 Sonnar lenses used to have their elements cemented into brass housings. These brass housings were then installed into the brass sub optical block.
Our method, is more like the ZK and Jupiter 8 lenses from the early 1950’s, which used Zeiss Jena glass confiscated by the Soviets, without the brass cemented housings. This is where the elements are not cemented into sub housings, but install directly into the sub optical block with retention rings. By doing it this way, I can adjust each lens to an effective focal length of 51.6mm much easier then the pre-war Jena retention method.
If you haven't by now guessed why we went down this design route, the term ‘51.6’ is key. I’ve implemented Brian’s method of adjusting the Sonnar lenses effective focal length, into the design from the get go. It is the only way to get the Sonnars to work correctly to focus down to 0.7m on Leica RF, since all optics have a tolerance zone they fall into, and I need a method to ensure a true effective focal length of 51.6mm is achieved each time. This is the genius of Brian Sweeney at play, in a lens built from the ground up, to abide by his white paper on how to modify their effective focal lengths. The same is true for all lenses really, modification of the distances between front and rear sets, is how true effective focal lengths are arrived at, which is often also noted right of the infinity symbol on most Leica lenses.
The aperture design, is also a direct copy of the pre-war Jena design. Both the aperture parts, and elements themselves on the Bertele, can actually be installed and mixed with the original Jena Sonnar elements with some element adapters I have, with no issue. Ive built up a few hybrids so far to my amusement.
This is where the similarities between the 1930’s Sonnar and our Bertele lens end. The glass used inside the Bertele, is modern glass made here in Europe, that contains no air bubbles obviously, and is not the soft type like the original was. It also has modern multi-coatings. The coatings are very similar to a famous manufacturers 1980’s and 1990’s lens range which I can’t mention. Needless to say, they have deep purple and blue hues, common to its post war ancestor... but also have orange, green and other wavelength specific hues in the coating mix, common to a more evolved form of its post-war ancestor.
The glass type, coatings and contrast, is the biggest optical difference, between the Bertle and the original Jena elements. In general, the Bertele elements are roughly on par optically, with the 1930’s and 40’s Jena Sonnar lenses, minus the coatings and the usual scratches and other issues one finds on copies that are 70+ years old. They render a more punchier and contrasty image then the original Jena lenses, entirely due to more modern coatings. In my experience with restoring and converting pre and post war era Sonnars, it is becoming harder and harder to obtain decent copies. The remaining decent copies, are becoming more and more pricier also.
The front of the lens is E39 filter thread, and has a notch for attaching a Wetzlar style hood (i.e. pinch on type made for E39 lenses). We have done away with the 40.5mm thread, to ensure a synergy of front filter usages for Leica RF users.
The body is nearly all brass. It feels better in hand when using. To counter the additional weight, the sub optical block is becoming more aluminium. Thus, with reduced sub optical block weight, the lens is easier to focus. We did have a prototype that was all brass, and it weighed over 330 grams. So the brass exterior, partial aluminium sub block housing, seems like the best compromise.
There is a plan to offer chrome plated versions, and various other colour cerakote options. The non-chrome painted versions, will use cerakote finish, since we can’t use anodising anymore since doing away with aluminium on the body. I’ve partnered with Aaron from camerakote, to provide the custom finishes for the Bertele, so something as wild as Caribbean blue, or themed colour combo’s are entirely possible (a sample photo of some pre-war Sonnars they have painted for us).
The optics, sub optical block, aperture system, are all done being manufactured.
The body is what is being finalised.
It is the body, where things will be different then any previous Sonnar. It is native M mount, has a recess for user added code (but will not be sold coded, to not violate any patents), focuses down to 0.7m, finger tab on the focus ring, and implements some new designs such as an anti-backlash system. It is most similar to the V4 cron body in its function and appearance. It is also made here entirely here in England, which is a double edged sword (more about this below).
Similar to the 8 element replica from light lens lab (which I have a copy of BTW, and love), we plan on offering customer engraving on the front ring also. The 8 element replica project, has been an inspiration for the Bertele project also, I must admit.
We have been meaning to provide an update in Q1 2021 about the Bertele project. The main hurdle I’ve had to contend with is Covid-19 this year, which hit right as we announced the Bertele lens. The United Kingdom has been one of the hardest hit countries with this, and we are in a second lock down now. Since our consumer camera lens manufacturing industry in the UK is basically gone (we have Cooke, but they make PL cinema lenses.. it has been a long time since Taylor Hobson actually made rangefinder lenses!); I have been trying to execute the desire and will of many British photographers, to have the Bertele lens made entirely here in the United Kingdom.
This has not easy when many local machine shops that make parts for us, are closed for months due to lockdowns. The ones that are open, have placed parts on long lead times, because automotive and aerospace companies simply have more money to throw at them to get their parts done at a priority turn around time. Covid-19 was the ‘monkey wrench’ in our Bertele manufacturing plan, and as such, there is no way for it to be ready by Christmas 2020. Im confident by mid 2021, some of them will finally be ready.
Im attaching a few images of the Bertele designs. There is a vide of the reverse engineered Jena aperture control system here also:
https://youtu.be/JwcNEQxSbbk
The project is more a labor of love then anything else. Many people who are involved with it on our end, simply love Sonnars. We want a vintage formula sonnar, with modern coatings, in a native m mount body, that is high quality and focuses down to 0.7m. Believe it or not, there isn't a Sonnar that exists like this, else we would all buy one and there would be no Bertele project...
Growing tired of using adapters, or installing Sonnars into other donor bodies for usage on Leica... we decided to simply just make our own to satisfy our own curiosity and love for them. If we can make a small batch of them, so others that want a simliar vintage sonnar in modern M mount body can benefit from our passion project, I’m more then happy.
These old formula lenses will never compete against modern ASPH APO offerings, they aren't supposed to. They make images that have a non-sterile, artistic value, that more and more people lately, seem to be desiring.
Over the next several years, our intention is to bring back ‘many’ of the Zeiss pre and war era formulas, into remade rangefinder lenses for Leica RF. There is another famous vintage Zeiss formula, already in the works, that is made to complement the Bertele as a ‘two lens RF solution’, but more about this one sometime next year.”
Chris
Skyllaney Opto-Mechanics
Warwickshire, England
