Between the Nikon F mount, Nikon Z mount, FTZ adapter, Metabones MFT to Nikon F mount, and Nikon TC-14e II, I have a serious amount of adapters and extenders to choose from depending on what camera I'm shooting on. Here's my $0.02 on dealing with the FTZ adapter on my Z50 and adapting glass to other cameras.
When the current generation of mirrorless cameras came out, I monitored closely the ability and the technology that the mirrorless adapters used to be able to mount old lenses on new cameras. While I'm a Nikon guy, I am frustrated that I can't use my meager collection of lenses on that whichever camera is in front of me at the time. I want to put my F mount glass on my Sony a7R III at work — why can't I do that? Am I shooting myself in the foot by using adapted glass all the time? If you don't want to read on, my answer is like my early 2000s Facebook dating status... it's complicated.
First off let me say the Nikon ecosystem has worked pretty flawlessly for me. All my F mount glass works on my Z50, and the Z6/Z7 that I have used and with that you get extremely quick and accurate auto focus on all of those AF-S lenses. This includes using the Z50 with the FTZ adapter and the Nikon TC on a 300mm F/4. While a bit cumbersome, the setup does indeed work and it works well. The latest firmware update for the Z50 allows me to do 3D-tracking style back button focusing which makes me very happy and is almost as good as 3D tracking on the current generation of Nikon DSLR. With center lock on tracking enabled, that focus sticks pretty darned well considering the cameras I'm comparing the Z50 to are much more expensive. Technical progress is apparent here.
So, the only Z-mount lens I own is the Z50 16-50 kit lens. I treat this lens as a body cap that can also take pictures. The lens itself is so small compared to the F-mount glass with the FTZ adapter attached that it is essentially, for me, a lens that gets mounted to store the camera and then the FTZ with my F mount glass gets installed for more serious photo shoots. The quality of the Z mount glass I've used is excellent and eventually I can see myself buying into some specialty glass in that system, but as you'll read — I'm not sure it's necessary.
Generally when building out a photo/video kit I recommend spending money on glass versus cameras. My thought is that the half life of a nice lens is much longer than that of a brand new digital camera. Lens technology has progressed, but much less distance than that of a camera body itself. Case in point, Nikon's F mount has been in use for over 60 years and the company has still found a way to make those lenses work on today's current systems. You are going to be much better off investing in lenses instead of the latest and greatest camera body generally speaking.
To prove my point further think of how many current motion picture cameras use Canon EF lenses in their systems. If someone today asked if buying EF glass was a bad investment, I would probably say it isn't considering Canon DSLR and lenses are still very relevant in terms of usability and utmost quality. Many other cameras including the Black Magic Pocket Cinema 6k go so far as to even use Canon batteries extending the life of existing camera technology. Camera manufacturers are doing this fairly well — and they need to unless they want to alienate their existing customers.
While the state of the industry is primed to change, I am very happy to see that the adapter industry has grown, learned, and made advancements that allow us to keep our investments in glass. When mirrorless cameras and new mounts were announced we were pessimistic about how our old glass would hold up. Little did we know that companies like Metabones would release speedboosters that allow us to shoot adapted glass at even wider apertures. My own Z Cam E2 M4 has only ever seen adapted Nikon F mount glass and I'm stoked that I get to keep some of my favorite full frame lenses in action and even enhance their maximum apertures from f/1.4 to f/1.0.
Do you have a good or bad experience with a lens adapter? I'd love to hear about it below.