The R7 does work very well with the the RF 100-400mm at f/8 and the RF 800mm f/11. Just because the R7 would work even better with f/2.8 versions of those lenses doesn‘t mean it works badly with those narrower lenses. There are 100s of images here and on Fredmiranda showing how good they are in practice. I’m afraid you have been in all of your posts “making the perfect the enemy of the good”.
If I had to make a choice among, say, the Sony A1 + 200-600mm, the Nikon Z8 + 160-600mm and Canon R5 + 200-800mm, I would choose the, wait for it, the Canon R5 + RF 100-500mm. All lenses are a compromise of aperture, focal length, mfd, zoom, weight, size and price etc. My ideal lens would be a 10-1600mm, f/2.8 constant aperture, macro to infinity, weighing less than a kg and small enough for hand luggage. Until @HarryFilm finally delivers one, I will stick with the RF 100-500mm as my main telephoto for Nature since it is much lighter than the other 3 lenses and I can hold it and hike for much longer, focus much closer and its blisteringly fast AF is great for BIF. I would, and do, use the longer heavier lens in more restricted cases.
It's very hard to support a company that does things like make a "1200mm" lens by starting with a $13k 600mm lens from a different mount, adds a permant 2x TC to it, bolts on a flange adapter, and then has the gall to charge $20k for it.
Given the same scenario, I would take either the Sony A7RV + Sigma 500/5.6 (which ridiculously weighs less the Canon 100-500 does, in spite of being nearly a full stop faster), or the Z8 + 600/6.3.
You needs differ from mine. I used to shoot the Nikon D850 and D500 with the Nikon 500/5.6, which is a very sharp and light prime. But, I found the RF 100-500mm just about as sharp and so much more versatile because of its zoom and close focussing I will never go back to a 500/5.6 or similar prime. However, other peoples needs differ and they would prefer a prime. Now tell me, do you actually go out shooting with a 500mm prime or a 100-500 or 200-600 etc zoom? Or, is it all hypothetical? (By the way, the A7R5 has such dreadful rolling shutter - ~100ms compared with ~16ms for the R5, it would be of no use to me).
Fair enough that you need a fast prime for dawn and dusk. But, it is as illogical to say that the RF 100-500mm is "overrated" because it doesn't fulfil all your particular needs as it would be for me to say the RF 400/2.8 or the 600/4 are "overrated" because they are too heavy for me to hike with and don't focus close enough for my purposes.
What do you define as "serious" wildlife work? I think most would agree that the guys shooting the David Attenborough Blue Planet, Planet Earth and Mammals series are doing serious work. They use gyro-stabilised cameras mounted on helicopters, digital cine cameras, high-speed cameras etc and spend months trying to get shots, up in the air, under water etc. They use ARRI Alexa, RED cameras (such as RED Weapon, RED Dragon), and Sony Venice, and Super 35mm film cameras, such as the ARRI ALEXA 65 or ARRI 535. Their default lens is the Canon CINE-SERVO 50-1000mm T5.0-8.9 (costing only £68,000). Unfortunately, with those T-stops that are close to those of the RF 200-800, it wouldn't be good enough for you and all those who require wider lenses and those guys can't possibly be serious.
I am a lightweight hobbyist and don't claim to be doing any serious photography. What you consider to be serious photography is your own definition, and thank you for providing it. I absolutely never suggested or implied in any way whatsoever that the 100-500 is on a par with the £68,000 Canon CINE-SERVO 50-1000mm T5.0-8.9, far from it, but just pointed out that the favourite lens of the real serious pros has nearly the same "narrow" T-stops as the RF 200-800!
I agree that if you feel you need a wide lens for dawn and dusk then it is your right for you so to do and it is the solution for you. I disagree with your use of “overrated“ and have pointed out the lack of logic in its use. I do not like your criterion of what is serious photography as it is arbitrary and judgemental. I have no more to say as it has become repetitious.
I definitely WANT to say something about those super-lenses that are coming BUT I will let the BIG ELECTRONICS BOYS talk first to the major news outlets as they use those fancy patents of ours in their upcoming prosumer and professional prime/zoom lenses and DSLR/Video camera products!
The A7R5 has a maximum fps in mechanical shutter mode of only 10 fps - if that's good enough for you, that is fine. However, I would recommend when you go over to Sony that you go for the A1 - it's the one up there with the Z8 and R5 for high resolution action and birds in flight.
ps, I have dug out the measured sharpness of the Sigma 500/5.6 on websites that do IMATEST.
If f/7.1 is too slow, is f/6.3 or f/5.6 fast enough? That seems an unsupportable position in terms of real-world use. If you need meaningfully faster than the RF 100-500, you need an f/4 lens. What f/4 lenses in Nikon’s lineup are superior to Canon’s equivalents? I sincerely hope your statement about a lack of, “…viable options from Canon for dawn and dusk that are competitive with Nikon,” is not based on a 1/3- to 2/3-stop difference.
) but dusk is a good time. There are so many opinions and as long as we are civilized at each other all is well. In fact Alan is not only civilized but very helpful too. He has made great suggestions to me (Also, Neuro always responds to technical/gear questions).
