Yeah, again most people. I'm in a boat on tripods, on land I'm on tripods and monopods exclusively. When I go handheld, I want to look handheld because I'm trying to shoot cinema verite. The term cinematic has been lost. There are all kinds of cinema. The point is to control the movement of the camera whether keeping it still or making it move. IBIS works against the way I work, so I don't use it. Most people can't seem to understand that. That's why Panasonic made the GH5S for the few like me who want total control over the movement.
See I want my footage to look like it was shot on a 16mm Bolex in 1960. By definition you wouldn't use IBIS to achieve that look. The handlheld footage, small sensor, heavy camera gives you a kind of stabilized shake when going handheld. You can't get that with IBIS even when locked down.
Go watch the "Salesman." Totally "haldheld," shoulder mounted. They said, "Da.. the tripods." Watch the footage from the John F. Kennedy campaign . . .
In other words footage that looks perfect doesn't work for me. That's why I use old lenses, vintage Canon FD glass only. (I'd love some old Takumars, but don't want to deal with the radiation-doped lenses. That's why those lenses are so sharp!!!! Hot, baby!!!!!) Modern glass is too perfect. Modern IBIS is too perfect. I want those flaws. Those flaws can be used artistically. Thus the true meaning of cinema is art, not perfection. All art is less than perfect, but technical perfection is not necessarily art.
Also in the boat there is lot of vibration, and the IBIS and vibration control I've used in the past has not been able to keep up. A hard bolted sensor looks way better when running on the river.
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If you can, rent them all and try them. I know Samy's out by me has a program where the fee to rent for a day is subtracted from the final price if I decide to buy. I feel like between those 3 specifically I'd lean toward the GH5. I've been exploring the idea of buying the Ursa Mini Pro for a while now and so far my only deterrent as been that Blackmagic has horrendous low light performance across all of it's lineup (although for what I primarily do low light is irrelevant).
Yeah, note I mentioned the GH5S. Also the Blackmagic Pocket 4k has a dual native ISO like the GH5S, giving it great low light performance. I don't do much low light either, but sometimes it would be nice to have a dual native ISO at sunset on the river, especially when using an old F4 70-210 Canon. I'm clawing for an much light as I can possibly get. I think the GH5S and P4K are more in the same league.