Extenders RF extender or RF 600/800 primes?

[guydunnuk]

So would it be better to just buy the RF600/800 or get a 1.4 or 2X Extender to pair with the 100-500? How good are the RF extenders? Thoughts?

 

[Jake Shoots Birds]

Actually the 800mm f11 becomes a 1120mm f15, but yeah, it's still an issue - though you can do it in good light.

I've been shooting with the 100-500mm w/ 1.4x TC this week and while you're at 700mm on the long end I would put the image quality above that of the 800mm f11, and not just by a little bit. I have the 800mm and shoot a lot of small birds and I find the feather detail to be better with the zoom+TC than I do with the 800mm. And while the aperture is still not as small as I'd like I can still shoot at less than f11. If you have the 100-500mm I would invest in the TC. If you don't, then you have to make the determination on how much more you want to spend to get a little better.

Not for nothing, but the other option is the R7 which turns the 100-500mm into a 160-800mm at f7.1 on the long end with no loss of quality. There are limitations to the sensor and buffer, but depending on what you're shooting if reach is all you want this gives it to you without loss of quality or MP's (compared to cropped mode on the R5).