Based on what I read in vlogs by wildlife shooters it is considered a very good lens, although slightly less sharp/contrasty above 300 mm, and obviously not great at AF-ing birds in flight, but that is a camera-thing.
F/6.3 certainly would have an effect, indeed, but at longer FLs, so does air quality etc., heat, haze, and what have you. Since the resulting MTFs are essentially additive, this has a relatively large effect on the system resolution, which is exactly what is shown in the lenstip chart.
As it is a rather extreme long zoom, it will not easily beat a prime anyway, that is to be expected. However, all in all, I reckon it is a great lens.
The 300 F/4 is in a different class alltogether, however. Based on my calculations it looks like it is very close to being diffraction limited from wide open, IOW, it is as sharp as it gets. I'd still have to see how it behaves on a camera wih a newer sensor, with higher resolution, but I do expect it to do as well.
HTH, kind regards, Wim
P.S.: Do note that the readings are done from the RAW-files. I'd expect for processed images to do better.
F/6.3 certainly would have an effect, indeed, but at longer FLs, so does air quality etc., heat, haze, and what have you. Since the resulting MTFs are essentially additive, this has a relatively large effect on the system resolution, which is exactly what is shown in the lenstip chart.
As it is a rather extreme long zoom, it will not easily beat a prime anyway, that is to be expected. However, all in all, I reckon it is a great lens.
The 300 F/4 is in a different class alltogether, however. Based on my calculations it looks like it is very close to being diffraction limited from wide open, IOW, it is as sharp as it gets. I'd still have to see how it behaves on a camera wih a newer sensor, with higher resolution, but I do expect it to do as well.
HTH, kind regards, Wim
P.S.: Do note that the readings are done from the RAW-files. I'd expect for processed images to do better.
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....