Short of LINAC irradiator ride-through videos on YouTube, are there any photos of this effect in air from a point source?

All the ones I see are reactors through water shielding, in which case you’d be fine.

If you see a noticeable cherenkov effect from something that close that wasn’t heavily shielded by something like water, your camera sensor will likely be destroyed and you’d be dead pretty soon.

Astronauts have reported having difficulty sleeping due to cosmic-ray-induced Cherenkov flashes in their eye bulbs.

The best comment on those videos:

“Worst Ride Ever”

Or unless it's in water, in which case you're actually probably fine.

If you swim too close to it, you might as well not bother to surface.

Yes, "too" close by definition would be a problem. But even a meter of water between you and the source absorbs 99.994% of the radiation (down to 6 thousandths of a percent vs in air, or by a factor of about 1/16000).

If the source is 16000x the exposure needed to kill you, then 1m will be too close.

In that case, I'm afraid your phone possibly won't function

Well… it might be a Nokia 2260