I own an R5 with a RF 100-500mm 5.6-7.1 L and a RF 1.4 extender. So, I can reach out to 700mm at F10. I am ecstatic with the results of this setup. But, I am considering the possibility of taking it a step further. My goal is to keep a similar reach, improve image sharpness, and improve low image quality. For example, I took photos of a Great Horned Owl in the blue-hour before sunrise. At 500mm and F7.6, I failed to get the results that I wanted. With the 1.4 extender, it would have been even worse.
My question is... is the RF 400mm 2.8L + Extender an equivalent ( or ever more versatile option) ) compared to a RF 500mm 4L or RF 600mm 4L? There is a tough balance in this question. Is the capability to go down to 400mm at 2.8L worth it versus the ability to extend to 1200mm at F8? ... length vs light?
