Tomfl101 wrote:
...16 megapixels and DX...you could do better with a full frame camera and 20+ megapixels....
Not true...
Just considering resolution alone, scaling up from DX to FX, 16MP on the former equates to 37MP on the latter.
A DX sensor has approx. 370 square mm of area.... divide 16,000,000 pixels by 370 = 43,243 pixel sites per square mm.
An FX sensor has approx. 864 square mm area... multiply 43,243 x 864 = 37,361,952... or about 37.4 megapixels.
For that reason, the 46MP Z7 would be a much better choice than the 24MP Z6.
HOWEVER, it's not only about the resolution...
For one, you shot that image at ISO 100, f/4 and 1/160. It probably would have been much improved by using one stop smaller aperture and doubling the shutter speed, which would have meant using ISO 400. A full frame camera like the Z6 or Z7 would make for less risk of noise being an issue at higher ISOs.
Another thing.... Lenses on DSLRs ideally should be calibrated because the autofocus sensors utilize light that's been redirected by mirrors. That's to fine tune the accuracy of the focus. But because the AF sensors in mirrorless cameras are embedded directly in the image sensor, on exactly the same plane as the image will be made, there's no need to calibrate lenses on them. As far as focus accuracy, you'll always get "the best it can be" out of any lens used on a full frame camera.
You need a MUCH longer telephoto lens! 16-80mm? That image you provided would have been a lot nicer if you'd used a 300mm or 400mm to get a much tighter shot of the eagle. Heck, at first I didn't even realize there was an eagle in the image!
With the 46MP Z7 you'd have ability to do some cropping, too, if needed. Even so a much longer lens for a tighter shot would have been better.
With the 24MP Z6 you would also need 1.5X longer focal length so that you don't need to crop... to get full benefit of the larger format, figure on a 500mm or 600mm to minimize cropping.
You didn't indicate the lenses you have. But, for example, if one of them is a 70-300mm on your DX camera, instead with a full frame camera you should plan on using something like the 200-500mm. That's trading a 1.5 lb., 5.75" long lens for a 5 lb., 10.5" long lens. That's doubling the cost too (even though the 200-500mm is offered with a big discount right now). Either lens would utilize the same FTZ adapter (adding a little length and weight).
Maybe you should consider sticking with a DX camera so that you also can use smaller, lighter lenses. Where you need 300mm on full frame, 200mm will do on DX. Where you need 500mm on FX, 300mm on DX comes very close. In a sense the DX format acts like a "free teleconverter" and for that reason remains quite popular for wildlife (as well as sports or anything else that requires a lot of telephoto work).
You could upgrade to a later DX DSLR. I'd recommend the 24MP D7200, though it's only available used now (has been superseded by the D7500, but that camera is in some ways a downgrade from the D7200).
Or if you prefer, might choose a DX format mirrorless such as the Z50 or Zfc (both are essentially the same 21MP sensor and AF systems... Z50 is basically a modern camera, while the Zfc is a retro designed to look a lot like and function a little like the FM2n SLRs from the film era).
It might not hurt that a DX camera like the Z50 is half the price of a Z6, about one third the cost of a Z6II or Z7, and less than one fourth the cost of the Z7II.
If you decide to go with one of the mirrorless cameras, be sure to confirm that your "older F-mount lenses" will work properly on it via the FTZ adapter. There are some limitations (I believe there is a new version of the adapter coming, which may change some things).