RF 400mm f/2.8 L + extender versus 600mm f/4 L ?

[jcass]

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?

 

[RedCobra]

Then there is the new RF 100-300 f/2.8 that takes TCs very well. 600mm at f/5.6 with a 2x on it.

I tried a friends R3 with the RF 400 f/2.8 and for me it was too heavy and unwieldy.

To solve this, I went into the M43 system and got a M.Zuiko 150-400 f/4.5 that includes a built-in 1.25TC that gets me to 800 at f/4.5 and 1000mm at f/5.6 FF equivalent on an OM-1 and it takes 1.4 and 2.0 TCs well. (1400mm at f/8 and 2000mm at f/11 with TCs))
And it zooms.
For me, the biggest issue with the RF 400/600 was weight. The Oly system with the big white, weighs less than the R5 with the RF 100-500.
(OM-1 is 20.4 mps with a BSI stacked sensor and up to 120fps and pre-capture))

Do I miss 45mps FF. Occasionally, but not often. Other photographers can't tell the diff between the prints a 13x19 from the R5 or the OM-1.
When I leave the house it's a dilemma as to which camera to take. R5 or OM-1.
Small sensor noise ( and it not that much different in real life) is easily handles by NR software.

Wait till you try to keep a bird in the frame at 1200mm. LOL

ps: I also got the M.Zuiko 300 f/4 (600 f/4 FF equiv) that came with a free 2x TC that gets me your 1200mm f/8

pps: Not selling my Canon gear. Next Safari I am taking both the OM-1 with the big white, and the R5 with some L lenses instead of 2 R5s.

Here is what you need for BIF at really long focal lengths. (not mine)

LOL

 

[MikeZ]

Nice photo chair/rig and a hell of a piece of engineering.

 

[jcass]

@RedCobra , thanks for the input. I wasn't considering weight. Good point. Unfortunately, I can't seem to track a bird in-flight at 16mm, let alone 1200mm. I'm new to birding and need lots of practice.

 

[freddijay]

My, my, my, my, my... that is one specialized and impressive piece of gear. I like the red-dot sight, screen magnification hood, and the gimbal setup. All it needs is some form of propulsion and bigger tires and it would be ideal. Having said that, I'm assuming it was built for someone who is somewhat physically impaired and it's a nice solution for such a situation. Wow!
Yes, BIF takes a lot of practice. It's not one of my strong suits for sure.