Steve Spencer
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 p.5 #19 · Thypoch Simera 28mm f/1.4 ASPH. Type II Review | |
And this might be a good time to share some of my thoughts about modifying Leica M mount lenses for mirrorless.
With Cosina Voigtlander (CV) lenses when they make lenses for both Leica M mount and mirrorless mount the lenses are often fairly different. Cosina has a pretty long history of making Leica M mount lenses and their M mount lenses seem to be very optimized for Leica M cameras. That means among other things, they are very small, have a very small diameter, and have a short focus throw.
When Cosina makes a similar lens for mirrorless it is clear they change the lens in a number of ways. They obviously change the registration distance so it mounts at a proper distance from the sensor, but they also add electronic contact and relay information to the camera. In addition, the design constraints seem to change too. They relax the criteria for diameter and weight. The mirrorless versions almost always have a larger diameter and filter thread than the Leica M versions and they always weigh more (and more than seems necessary just to shorten the registration distance). They also shorten the minimum focus distance (MFD) and lengthen the focus throw. Sometimes they even change the aperture blades and in at least one case (the 50 f/2 APO, the optical formula).
Let's look at a couple of examples. The 21 f/1.4 Asph for Leica M has a 69.5mm diameter, weighs 480g, has a .5m MFD, and has about a 90 degree focus throw. The 21 f/1.4 Asph for Sony has a 70.5mm diameter, weighs 560g, has a .25m MFD, and has about a 130 degree focus throw. With these two it is one of the rare cases where the filter diameter stays the same.
The lenses are not hugely different, but they are different and personally I would prefer the E-mount version on a Sony camera and the M-mount version on a Leica M camera even if the performance was the same. I am glad for the additional changes in addition to the registration distance and the adjustment for the thicker sensor glass on the Sony camera.
If we look at the two versions of the 90 f/2.8 APO-Skopar, the physical differences are even more apparent. These differences are no doubt more extreme because we are comparing a Leica M lens to a DSLR lens. Still they share the same optical formula.
The Leica M 90 f/2.8 APO-Skopar has a 53mm diameter, weighs 250g, has a 39mm filter thread, about a 100 degree focus throw and a nifty 10 blade aperture that is round at f/2.8, f/4, and f/22, but not at other apertures. The SLII version of this lenses has a much wider 66.3mm diameter, weighs more at 260g (despite have a much longer registration distance), has a 52mm filter thread, and about a 180 degree focus throw despite having the same .9m MFD. It also has 9 rounded aperture blades. Optically, these lenses are the same and they have each been adjusted for their sensor cover glass, but physically they are very different. One optical consequence of the very different diameter is that the SLII version seems to have much less vignetting.
Cosina seems in my view to have carefully thought about making each lens not only optically but physically for the camera for which they design the lens. Even mirrorless lenses for different cameras can be notably different (the Sony E-mount 50 f/2 APO has a smaller filter thread than the Nikon Z-mount 50 f/2 APO). I like Cosina's approach and although I find Leica M mount Voigtlander lenses generally pretty useable on Sony E-mount cameras, I almost always prefer the lenses Cosina has made for Sony E mount. I appreciate not only the electronic contacts, but also the typically shorter MFD, the longer focus throw, and even the larger diameter if it reduces vignetting (I find Voigtlander lenses to be pretty extreme in their amount of vignetting). Larger diameter bothers me close to zero on a mirrorless camera, but if it blocks the viewfinder it is a critical issue on Leica M cameras.
What does this mean for Thypoch Simera lenses? Thypoch made the 28 f/1.4 and 35 f/1.4 for mirrorless mounts, but I am hoping that was mostly a beta version. It appears all they did was change the registration distance and put on the appropriate mount (and likely adjusted the optical formula for thicker sensor cover glass, but is that different for Sony E and Nikon Z mounts that themselves differ?). I would love to see Thypoch revisit these issues and make mirrorless versions of their lenses that not only get the registration difference right and provide optical adjustment, but tailor the lens for the mount. I would love to see electronic contacts, but I would also like to see longer focus throws (they do that already on the Simera-C lenses), and perhaps wider diameters if it reduces vignetting. I know personally, I would be a lot more interested in these Thypoch Simera lenses with a bit better tailoring for mirrorless cameras.
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