Measuring from the film plane:

If I want certain parts of a shot to be in focus while other parts are blurry; I have to choose the right lens, the right distance from the main subject, and the right T-stop (f-stop).

The ASC (American Society of Cinematographers) Manual has charts which tell me what I need to know, I just have to make precise measurements to make it happen.

In this shot the main character’s shoulder will be in the foreground (blurred) while the man at the desk is in perfect focus and the stuff behind him is blurred.

And I’ll be moving the camera behind the actor on a dolly-track.

There is no AUTO-FOCUS on a motion picture camera. Focus is manual. So you have to get the math right or you end up with useless film.

And that is a very expensive mistake to make.
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The white rectangle in the air behind my head is a silk. Silks are used to soften light and eliminate shadows. We have two 5,000 watt lights outside the window (it is night time but look at the window) and four 1,000 watt lights in the room.

And I still wish I had more light. We had to run a generator because the building's wiring wouldn't handle the electrical load from the lights.