Canon RF 100-300 f/2.8 IS USM

[Joel Eade]

Here's a quick comparison, and I think the 100-300/2.8 + 2x holds up very well compared to the 600/4 II. The 100-500 is no slouch, either...

https://www.canonrumors.com/forum/th...-is-usm.42653/

In those images, I would agree. Those are more of a "bird-scape" style .... my preference with birds to have the subject much bigger in the frame in which case the new 100-300 with the 2X TC may do just fine. Since I already own a 600 f/4 and the RF 100-500 it's not really a lens that's on my want list although it is clearly a stellar piece.

[neuroanatomist]

In those images, I would agree. Those are more of a "bird-scape" style .... my preference with birds to have the subject much bigger in the frame in which case the new 100-300 with the 2X TC may do just fine. Since I already own a 600 f/4 and the RF 100-500 it's not really a lens that's on my want list although it is clearly a stellar piece.

If not for this contrived 'test', I would not have brought the 100-300 on a birding outing at all. Outside of testing of this sort, doubt I'll use it with the 2x TC in the future. I can see using it with the 1.4x TC for outdoor field events, a 140-420mm f/4 zoom will be useful in that setting, and under non-pro field lighting the 100-500mm needs ISOs of 12800-25600, so the extra 2/3 – 1-2/3 stops of light will make a meaningful difference.

[Joel Eade]

Makes complete sense to me!