Camera (webcam or camera module) throttling

Hello all,
I've a Raspberry Pi v3B and when I connect either the camera module or a USB webcam I get the message that the
"Your Raspberry Pi is reporting insufficient power. Switch to an adequate power supply or risk bad performance and failed prints"

I've tried different power supplies rated 2.1A at least. And different USB cables with no change.

And yet another case of underpowered Pi.
I measured the voltage and it was slightly below 5V (around 4.7V).
An Apple power supply works great.