One of the trickiest things as a performing arts photographer is going into a theatre or concert hall you haven’t worked in before, and trying to pick the right places to be, and which lenses to use, for a show.

In most situations, I have two camera bodies on the go at any time, so I can have different lenses mounted on each of them to cover a wider range of fields of view—and of course so that if one camera has a problem of some kind, I can immediately switch to the other one. (Fortunately that doesn’t happen very much!)

But going into a room I don’t know is a special challenge, especially if I’m photographing while there’s an audience watching. If I have to stay out of sight and not disturb anyone, then I probably need longer lenses than I would if I can be right up at the front of the room capturing tight portraits of the performers on stage, during a rehearsal.

So, how long is long enough? And how do I work that out ahead of time, so I know what to bring?