I never hesitate to use the 100-400 L II, instead of the corresponding prime. Canon's telezooms are as good as most primes. Canon's 70-200 are in the same category, superb, optically and mechanically.
I'm not sure if your preference for the 5.6 was on speed, DOF, or weight as compared to the 100-500. If in term of speed, the newer camera handling of noise on higher ISO was decent, all you need is just bumped the ISO setting to compensate for the 2/3-stop lost of speed.
The 400/5.6 + EF-R adapter weigh 1460g compared with the RF 100-500mm + hood+tripod foot at 1610g, which is not exactly beating the hell out of it at 150g or 5.3oz less on that weight. The RF 100-400mm weighs in at 690g including IS, which does make a real weight saving.
One of the things I loved about the 400 f/5.6 was its simplicity. 7 lens elements, that's all.
Canon hasn't refreshed the 400/5.6 for more than 25 years and the 300/4 for nearly as long, which speaks about their philosophy. Nikon has made some rather nice small light primes. I wouldn't trade the 100-500/7.1 for a 500/5.6L. I used the the 100-500mm zoom on the R5 and the 500/5.6 on the Nikon D850. The zoom was so much more versatile and so close in sharpness to the prime, it was no contest as far I am concerned but YMMV.
Well I never said it was the ultimate for birds in flight and my RF 200-800mm f/6.3-9 is great for that (I have no trouble tracking birds with it if they're flying straight) as I very rarely try to shoot BIF in the dark of the rainforest so a very bright aperture isn't needed.
It depends:
Have you tried the C.Fn to maintain “Same expo. for new aperture”? Might not be what you want, since it adjusts shutter speed or ISO to compensate.
Ahh interesting – I never knew of this feature – a bit different than was describing, but definitely useful in other circumstances – thanks for the tip!
On the camera side, yes that makes sense. The lens that comes to mind as a (slight) problem in this regard is the Zeiss 21-100 T2.9-3.9 ... admittedly a manual lens ... not sure if there are any electronically-controlled aperture lenses which have this characteristic.
Considering that the EF 200-400 f/4 is around $11K, I think this is, alas, way past wishful thinking. Especially when requiring it to resolve at least 45Mpix when paired with a 1.4x TC.
Given that 500mm f/5.6 needs front element diameter (ignoring that rounding that always happens) of only 0.3mm larger than 800mm f/9 (i.e. the current RF 200-800), it could come in at around $3.5K or less for an L lens, or around the price of the 200-800 if a non-L. But I still don't see the point in such a lens, given the existence of the 100-500L and the 200-800.
I agree, there would be no point in a 200-500 f5.6 given the existing 100-500 L. Unless, of course, Canon reads all these forum threads where so many people are under the illusion that 2/3rds of a stop faster makes any sort of meaningful difference.
To each their own.
They wouldn’t use the forum threads specifically, but if they feel they’re losing a segment of their market share due to a perception of the competition offering a better product, they’ll probably react (much as they did with the 70-200 2.8 Z)
