Good light in the morning and mostly sunny skies in the afternoon gave me a chance to do a direct comparison of the a7 IV/100-400mm GM/1.4X and R5/RF 100-400mm/1.4X. The short answer: Canon. Read on for further babble on the subject.
While the Sony zoom alone is a tiny bit better than the RF zoom, as well it should be for more than 4X the cost locally, the RF zoom works a bit better with the teleconverter. While I really like the A7 IV, features like “Clear Image Zoom” make it seem like an amateurish body compared to the R5.
Trying to remember what my impression was of the 100-400mm GM the first time around, I now recall that the reason I ditched it after about eight months was because the 1.4X was not available anywhere during that time. Second time around, I believe I found the 200-600mm more impressive than the zoom/TC combo.
This time the only thing that’s wrong, really, is that a much lighter, cheaper “enthusiast” zoom clearly outperforms it when a teleconverter is attached. As I suspected, and others opined, some years ago, it almost looks as though Sony didn’t bother to create any stabilization algorithm for the lens firmware whenever the teleconverter is attached. Interestingly, it’s sharper when mechanical shutter rather than electronic shutter is used.
While the Sony zoom is superb at MFD, I’ve lost shots because it balks at searching near MFD, same as Nikon’s 300mm PF lens. But the Canon is no slouch close in either, and gets there quickly, almost instantly in good light.
Funny . . . when I first started considering options for my “lightweight backup” setup, the 70-350mm was one possibility that crossed my mind, ruled out because it doesn’t take any teleconverter. Although I previously mentioned it as being more than a notch down from the RF zoom, comparisons from the past couple of days show it to be almost as good. Not quite, but almost.
Do I sound confused here? Yes, you’re right . . .