The first sitting tells you who someone is. The second tells you who they've become since.
Alex Blake came back to the studio recently for an update to his headshots — the kind of return visit that punctuates most working actors' careers every two or three years, when the credits have grown, the face has settled into something a little more itself, and the agent has started asking gently whether the current image is still doing the work it ought to. Alex's was, mostly. But "mostly" is the word that brings actors back.
A short note on returning sitters, because they're a particular pleasure of this job.
The first time you photograph someone, half the session is reconnaissance — learning the architecture of the face, finding the angle that wants to be found, working out which side they unconsciously trust and which they've spent thirty years apologising for. By the second sitting, that work is already done. The conversation can start at what's changed rather than who are you. You can attempt things that would have been speculative the first time round. You can also, if you've been paying attention, see in the face what the intervening years have written into it — which in Alex's case is quite a lot.