What if you shoot an event in a dark room?
First, set your ISO-Aperture-Shutter combination to something you desire – in my case that is -2 stops metered w.r.t. ambient. E.g. 1/30th second, f/4. and 800 ISO in a dark, dark room like the venue Many options. where I shot a corporate event yesterday night.
But then you do need flash light to fill in the rest. And what if you cannot bounce? If the venue, like mine, is black, with high black ceilings and all black walls? You curse inwardly, of course. And then what?
In my case, in a total no-bounce environment I use this: A Fong Lightsphere with a Honl Photo reflector behind it:
Which gives me not the very best light, but it is, I think, perfectly acceptable:
Many other techniques also, but that will come another day.
And all that in a no bounce environment – which goes to show, you can always do something!