Is the new Nikon 600mm f6.3 PF a full 600mm at MDF? It’s my understanding that the Nikon 180-600 is but the Sony 200-600 is not.
What do you mean by "full"?
The answer can be longer than several pieces of string.
I speculate what you want to know is do you get a 6 wide or 12 inch wide subject at minimum focus distance –
often important with bird photography.
Going back around 60 years most lenses focused by getting physically longer.
A 50 mm angle of view at Infinity was likely to change to 55 mm or more by minimum focus, and so on.
The narrowing of the angle of view by minimum focus effectively changed the size of the aperture relative to infinity focal length - and a little less light was transmitted to what was then film.
Around 40-45 years ago, Canon introduced internal focus telephoto lenses which focused much closer than helicoid type but significantly widened their angle of view by minimum focus distance.
I recall buying a 400 mm IF around that time and being most unhappy when at a similar close focus distance it covered a wider angle than my 300 mm Olympus helicoid at the same close focus distance
About 20 years ago in the era of lenses like the Nikon 18–200 mm, angle of view could sometimes widen to double by minimum focused distance – accompanied by around one stop change in effective aperture!
With the Z lens range Nikon has set out to reduce or eliminate focus breathing, implying what you get at minimum focused distance is a similar or the same angle of view as at infinity.
Overall I find this to be true.
Trying to answer your question!
What seems to be true from many reports is that you get more magnification (a narrower angle of view) at minimum focus 600mm with the Nikon 180-600 than with the Sony 200-600 at a similar focus distance.
Nikon usefully quote a maximum reproduction ratio of 0.25 at 600 mm for the 180-600mm you mention.
For those who do not know, dividing the FX format size of 1.5 inches wide by the 0.25 maximum reproduction tells you how wide the subject will be – with an answer of 6 inches wide.
As an owner of this lens, I confirm 6 inches wide is right.
Nikon quote the maximum reproduction ratio for the 600 mm f6 .3 as 0.15 - a 10 inch wide subject.
Note the MFD for the prime is almost double the MFD of the zoom - still indicating a close to equal angle angle of view at each lens MFD despite the difference in image size.
IMPORTANT for the relatively inexperienced - minimum focus distance differences can significantly affect the maximum reproduction ratio (magnification) possible with different lenses even when the angle of view is close to the same.
Comparing the Z 600mm f6.3 and f4
specifications Nikon quote 0.15 maximum reproduction at 4 meters MFD for the f6.3 - and 0.14 at 4.3 meters for the f4 - close to the same angle of view at their respective MFDs and - as with the 180-600 - close to 600mm angle of view at infinity.
Speculating on my part -
- it is probable some (as distinct from all) competitors longer focal length lenses with makes with less emphasis on "reduced breathing" become slightly wider angled than Nikon with less subject magnification by MFD.
Even so it is probable that my long gone Olympus 0M 600 mm f6 .3 helicoid focus had a little more subject magnification than the Nikons at the Olympus minimum focus distance of 11 m.
Summing up -
- when minimum focus magnification is important, once the relevant information has been established – which is not always easy – a better informed decision can be made.