Hello Colin,
The image I posted is about 60% of the original, ISO 200, speed 1600 at 5.6.
The lens behaves like the 300 PF, I find the AF relatively fast and accurate, I use it handheld and, for the money, is a good buy. Due to a lucky coincidence
I paid 2,700 e for a copy used once or twice.
It is my first lens at this focal length and I can shoot from distances I could not do before. If you shoot wildlife (and close ups)
It is worth the expenditure,as I find it produces very good results. I have not tried the 1.4x TC on it yet, but at f/8 AF and quality will suffer a bit.
The image below is uncropped.