And given that the police can use laws that don't exist as probable cause which leads to an arrest and conviction [0], I don't think it's unrealistic to expect cops to say "well I
thought [the guy filming me from 30 ft away] was too close" to justify an arrest.
Sure, you might be found innocent (on the filming charge), but that's not the point - the cops wanted to stop you from filming, and they won. They might have even seized your phone and deleted the footage, and you have no recourse thanks to qualified immunity [1]. Just you getting thrown in jail and missing work could mean getting fired, being unable to make rent, getting evicted, etc. It creates a chilling effect, which is exactly what they want.
> It's also in violation of the 1st amendment, as many of these pro-policing laws tend to be.
It is, but sadly, SCOTUS will likely find some insane argument to uphold it.
[0]: https://en.wikipedia.org/wiki/Heien_v._North_Carolina
[1]: https://eji.org/issues/qualified-immunity/