With the introduction of new lens mounts for mirrorless cameras, everyone wants to combine lenses and cameras that ordinarily wouldn't fit together. But while some ideas are possible, not everything will work.
Years before I became interested in photography, I was a big fan of the Apollo space missions. I saved newspaper clippings and watched as much as I could live on TV as a kid. While it received less coverage than the moon landings, the subsequent Apollo-Soyuz Test Project maintained my interest. Conceived as an expression of Detente between the United States and the Soviet Union, the mission took place in July 1975. Using a specially designed docking collar, the team connected an Apollo capsule to a Soviet Soyuz while in earth's orbit. Technically, the rival space programs came about with no thought of being combined. It was only through clever engineering that the rendezvous occurred, and the impossible became possible. No further crewed US space flights happened until the first Space Shuttle took off in April 1981, about the same era I owned my first camera. Of course, it was a coincidence, but it forms a nice segue for our story here. The problem of connecting disparate camera lenses and bodies may not be as complicated, but it's no small feat.
While I owned a couple of consumer-friendly point-and-shoot models, my first serious camera was a Nikon, and I've stayed with the Nikon system ever since. I chose Nikon when I became an SLR owner because Canon had just converted from their legacy FD-mount to the EF-mount they've been using throughout the SLR era. Many photographers were mad at Canon for suddenly making their investment in lenses obsolete, and Nikon pledged to retain the F-mount. I felt safer with Nikon because of this. I like Nikon.
It was still a surprise when Nikon came out with DX-format lenses to match the smaller sensor size used in affordable Nikon bodies twenty years ago. They were still F-mount lenses, but they projected a smaller image circle than previous lens designs. Mounting a standard Nikon SLR lens on a DX body merely caused more of the image produced to spill over and not be captured. We expect some cropping. After all, camera sensors are rectangular while lenses are round. But the smaller sensor cropped more tightly. But mounting a DX-lens on an FX-body would likely result in a circular image or darkened vignetting in the corners. The two formats aren't fully compatible.
Now, we enter the era of the Z-mount that mounts differently than the F-mount. The flange diameter has a larger diameter. DX lenses physically fit on Nikon film SLRs, but they didn't necessarily work satisfactorily. Z-mount and F-mount components won't connect at all.
Even if they could, there's another major hurdle to overcome. Mirrorless bodies are generally more compact than their mirrored cousins, since they don't need as much space inside. Because of this, Z-mount lenses expect a shorter focus distance from flange to sensor media. Even if you could attach an F-lens to the face of a mirrorless body, the image wouldn't focus. Nikon solved this problem with the FTZ adapter that pushes the mounting flange out to the proper distance, allowing room for older lenses to focus where they should. Like the Apollo-Soyuz docking collar, one side of the FTZ has an F-mount bayonet, while the opposite side has a Z-mount opening.
Unfortunately, the reverse isn't possible. A Z-mount lens on an F-body would focus well in front of the sensor. A theoretical ZTF adapter (Z-to-F-mount) would move the focus point further away, regardless of the design. Perhaps someone could invent something akin to a teleconverter that used glass elements to refocus the image, but the quality would suffer. Once again, the two formats aren't fully compatible.
During the 1990s, together with partners worldwide, the United States and Russia launched the components that would form the International Space Station (ISS). Conceived as a cooperative laboratory and observatory in space, the ISS grew out of aspirations first expressed during Apollo-Soyuz. The ISS project involved at least fifteen countries, allowing for the interoperability of widely disparate technologies.
Akin to the ISS, maybe the world needs a universal format compatible with all conforming lenses and bodies. Surprisingly, since August 2008, when Olympus and Panasonic introduced the Four Thirds System, we've had such a thing, but it's never really caught on. Give them credit for trying, but the design proved too limited. Four-Thirds sensors are even smaller than Nikon DX, likely perceived as a compromise between APS-C formats and even smaller compact digital formats. They weren't forward-looking enough, given today's trends towards full-frame. Four Thirds also presupposes greater openness and cooperation between vendors than is reasonable in the competitive world that camera makers inhabit. It isn't as bad as the Cold War between the United States and the Soviet Union. But now, the fierce competition is over corporate, not national pride. Some things are possible, but don't expect too many miracles. Competition spurs innovation but can inhibit cooperation.
Or, maybe we need a system of adapters similar to the T-mount system introduced by Tamron in 1957. As a third-party lens manufacturer, they needed an economical way to produce lenses for a broad cross-section of a market spanning multiple camera brands. The result was a line of adapters with a Nikon, Canon, or other branded mount on one face, and a universal Tamron-designed T-mount flange on the other. Tamron could then produce a single lens in each focal-length category and sell it to photographers, no matter what brand they shot. But the T-mount specification was fully mechanical, so it was eventually left behind by history as cameras adopted electronic interfaces.
A modern, electronic version of the T-mount might be possible in some limited fashion, but I wouldn't hold your breath waiting for one. Once again, the problem stems from secrecy and competition. A limited amount of detail on Nikon or Canon's electronic interface is available for license under non-disclosure to allow aftermarket companies to create compatible products. But each company holds back some specifications, considering their trade secrets. As in the race for space, cooperation and competition are often at cross purposes.
But for now, mirrorless shooters benefit from a window of detente. The space afforded by the focal distance change from F-mount to Z-mount creates a chance for incompatible systems to be bridged. A growing number of third-party companies now produce adapters similar to the FTZ, allowing Z-mount users to use lenses from companies including Sony, Pentax, and Yashica. Not every combination is likely, but it's surprising how many are. It makes you almost believe in miracles.
In part because of the invasion of Ukraine, the future of the International Space Station seems somewhat in doubt today. Cooperation tends not to last forever. Competition and rivalries get in the way, eventually. We live in a complicated world, and our cameras reflect that.