I mentioned diminishing returns if putting a 2X to a f/7.1 lens making it f/14.2 on a 90mpixel FF camera. That's all!
Thanks for your clear answer.
However, I am as well an amateur astronomer. If you look through a telescope you will seldom, even with an apochromatic objective (i.e. the best there is) get more details on an object if you magnify it by more than about 20X/cm the diameter of the objective lens due to diffraction starting to get visible.
I.e. with a 10 cm objective lens when you pass 200X magnification.
If you let us say increase the magnification to 400X , you will not see more details than with 200X, rather you will see less. The reason being that you do get a more enlarged view, but the sharp defined details you had at 200X are now lost into a more "fuzzy", unsharp image. Actually it can mean that you at 400X even lose details, e.g. let us say you are just only glimpsing a certain weak moon of Saturn at 200X, at 400X it may be very difficult to perceive it any longer as it has become even weaker as the same amount of light as before now is smeared out.
That was really my question as regards the R5s in combination with the RF 800/11. Will I only get the same amount of details as with an f/5 lens?
I.e. I will not get anything more as regards added details?
Thus no great idea to consider RF 800/11 as a smart extra investment??