As I said, I did not want to question a proper test [+].
Unfortunately, up to now, no reliable data on the optical performance is available for the 560/5.6.
Surprisingly, the most impressive pictures to date are taken
of the lens and not
with the lens.
Even photographers with experience in shooting with ultra tele lenses have not shown really good examples yet.
See, e.g.
First DA560mm shots PFC - Pentax Fans Club 300 400 560 250-600 - Pentax Fans Club falconworld
It remains to be seen how the DA 560 performs against the F(A)* 250-600, F(A)* 600, Sigma 500/4.5, (F)A* 300/2.8 + 2x (or cropped), Sigma 50-500...
Some theoretical data on the 250-600:
#208,
The Lens Design of the 250-600.
Sigma
50-500,
300,
500.
I could not find MTF diagrams for the FA* 600/4 or the FA* 300/2.8 (test winner in German ColorFoto 1/2001).
Is there any official data published by Pentax?
[+] Rating lenses primarily on real-world examples is also not a good idea.
Good pictures might be more related to the capability of the user.
High-end gear does not per se guarantee acceptable pictures.
Outstanding pictures do not necessarily require high-end gear.
It would not be a wise decision to buy a lens because of one or more reference images.
This also questions the usefulness of threads with example shots taken with a specific lens.
I am not convinced that somebody could identify a lens only by e.g. micro-contrast, colour rendition, bokeh, flare resistance, CA, etc.
Maybe a dedicated thread ("Identify the lens") with samples would be a good idea.
However, I have not yet seen a single convincing picture taken with the DA 560.
This might be due to problems of handling (balance, center of mass, tripod mount) or due to other issues.