I just wanted to chime in with a more detailed explanation of the 6K photo mode, which can also be used for 5K video (with 1:1 pixels).
There is unequivocally no upscaling or downscaling in this mode. And if you shoot 5K video in this mode, you have extra pixels on the vertical to allow you to decide precisely where you want to crop out the 5K video. And you can also use the extra pixels to do some image stabilization in post, and still retain 5K video quality.
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It's really impressive but for me the most important features won't be added until summer, so I'll wait until summer. Maybe by then, Sony will release another monster to fight with the GH5 and we will have another better option, or the GH5 price will drop.