https://marco.org/2007/11/07/my-apologies-for-the-technical-flaws-of-these
My apologies for the technical flaws of these Meetup photos. There was hardly any room lighting, the speakers’ faces were completely dark, and and they were backlit by a giant bright projection screen. I had to be wide open at f/2.8 and ISO 1600 to get a reasonable speed, and I often had to overexpose by +1 or +2 EV just to get the speakers’ faces to have any definition at all. And I was sitting right in front of them.
Any advice from pro photographers, besides using flashes or expensive f/1.2 primes?