I’m looking for advice on how to build out additional equipment for wildlife. Currently own A7riii + Sigma 100-400, plus EM10.2 & GH5. I want a smaller system, and I’d like to start doing BIF. I like taking both videos and stills. It seems that the PanaLeica 100-400 is the best option for me. Top tier Panasonic stabilization, weighs less than my current lens, and gets me to 800mm. I would expect the AF performance with a GH5 to be better than my current system in many situations. Perhaps add a EM1.2 down the line to get the better AF and lower EVF lag That said, I do want to double check some of my assumptions, & where I can go next after the PL 100-400. I don’t think an equivalent lens to that PL100-400 will come out for any other system for some time (closest would be RX10iv and Nikon 300PF, the former doesn’t go to 600 and the latter requires swapping TCs, including a 1.7x). For M43, my understanding is that the only upgrade path will be to that 150-400 that’s coming out someday (the 300mm is a sidegrade with more IQ). My current system: The Sigma 100-400 doesn’t have a fast enough motor for me, and the 600mm effective focal length is not enough for the perched birds around here. 1.4x teleconverter is not usable on my hardware. The lens + adapter also weighs 2.75 lb. It’s really hard to use for handheld videos. In terms of my experience level with various equipment, I’ve shot a few weekends with the Sigma 150-600 and Panasonic 100-300 on EM10.2 and GH5, and rented a couple of current gen Nikon and Canon bodies. I liked the Panasonic 100-300 form factor, but the stills IQ at 600mm (effective) was too soft for me even in good light, and the Dual IS at 600mm (effective) micro-jittered in videos even with IS-Lock mode on GH5. That said, I was actually quite pleased with how good the videos are for such a small system / long focal length. Thoughts on other options: Fuji seems like a dead end. It has few options beyond 100-400 Canon - less recent investment than Nikon in enthusiast lenses for wildlife. Their small primes are really old Nikon seems like a pretty reasonable way to go, given how nice their super-telephoto lineup is. I could definitely see myself getting a 300PF, 500PF, or 150-600 down the line. Now, having three systems could be a good or bad thing, depending on your perspective. D500 - really liked that camera, a little bit heavy D7500 - save $500 and 100g on for other lenses Sony also seems like a pretty good path, since I plan to maintain that system long term for portraits and general sports. That new 200-600 is a great value for $1999 for people that are already in Sony.