To capture any 4K ProRes footage with 128GB 15 Pro you need an external drive, this is presumably because 128GB model has a single memory chip and data write speeds are insufficient.

I might be doing something wrong, but when I tried to set BlackMagic Camera to ProRes Log 4K60 it had no problem recording it. I was even able to apply different free LUT files and export it to photos. It is 1.6Gb for 8 seconds, but did not require an external disk. [1]

[1] https://imgur.com/a/9vUdPcg

Edit: iPhone 15 Pro 128G

Huh, interesting, I just tested it too and does work in Blackmagic camera (iPhone 15 pro 1TB). I guess it’s only a limitation of the official Camera app while 3rd party apps can do otherwise.

Wow, very nice, I didn't know. Thanks for this feedback!

Is that Mb or MB?

4k30 Log is approx 100MB/second