The FTZ adapter has no aperture lever. One is forced to use old Nikon MF lenses, or brand new Zeiss lenses, in stopped-down mode.
This is a mixed blessing (ahem):
+ when focussing a stopped down lens, focus shift is no longer an issue, but
- accuracy of focus is less, and
- the EVF needs more amplification, which may lead to a degradation of the image in dark places, again making the focus more difficult
- no aperture info is provided in the EXIF or in the viewfinder
The last and next to last drawbacks are two of three reasons why I refrain from buying a Z model. The image degradation when the EVF amplifies its signal is really significant, and comes in addition to the fact that the EVF cannot compete with an OVF to start with.
Some purists will likely interject that EXIF data are not necessary and that one should concentrate on image content and forget about technical data. To this, I strongly disagree and see no reason why one should throw away a true advantage to digital camera technology. I consider the image degradation caused by the stop down metering the decisive reason why I stay away from the mirrorless offerings, though. Also important is the much shortened battery life.
On balance, I find no really weighty reasons to go mirrorless unless video use is paramount.
Per Inge Oestmoen, Norway