Running 22 episodes per season on network TV, Person of Interest didn’t have money or development windows or shoot time of a bigger show.
Episodic directors must understand when and how to maximise big camera moves; often less about the shots themselves, more about how they work within the whole. For example a wide drifting dolly shot contrasted with static closeups can show one character moving forward while others are stuck. (And those static shots may be a necessity if you blow a whole day on a big expensive dolly move.)
The final amplification of trickiness is network shows are EXACTLY 42 minutes; you can’t just run 46 minutes this week if a oner pushes the episode long, you’ve got to trim those four minutes elsewhere.
With all that, why did director Kevin Bray decide this oner in Person of Interest 4.13 “M.I.A.” is worth it? Watch Dani Silva (yes, that’s Adria Arjona, in a recurring role) do her thing, then we’ll talk!
From a practical standpoint, this isn’t necessarily a blowout shot; eg. lighting the whole room at once can sometimes be quicker than lighting eight different setups. On the other, more complex, hand are bigger location and/or set construction requirements; longer choreography time with actors and steadicam operator; a flubbed line, missed mark, or bad focus pull causes countless resets and overtime, etc. It adds up quick!
From a creative point of view, moving through darkness and [relative] light and colour changes is aesthetically pleasing, and allows for the possibility our villain is going to emerge from anywhere. As the camera backs up from the bathroom door we see a floor-length curtain and think surely our bad guy is behind it . . .
except wait, here he comes from behind the audience / camera!
Now he opens the door, knowing exactly what we know about what’s happened since it closed, and SURPRISE!
The oner is a good ‘excuse’ for (or rather, answers an audience’s potential objection to) ‘why don’t we see what’s happening behind that door’ in the between time.
While the ‘reveal’ may not throw anyone who’s been a fan of the show, it’s about building up to a moment, driving excitement with an unbroken shot which adds new information through choreography instead of cuts.
When the action goes down, its quickshortsharpshock edits, closeups, and rapid camera moves work partly because they’re in contrast to the long, slow tension from the first half of the scene.



Takeaways
To get maximum effect from your more complicated and costly shots, pick and choose not just where to use your oners to best effect, but what you put around them.
Last, don’t forget about blocking specific beats; I love how the blocking places Dani’s face over the split in the mirror in a ‘whose side will she end up on?’ moment, which is something you could more easily do in a static shot, but they still manage to get in the oner.