Question: When Nick goes to the restaurant when it is closed for the day and night, and Nick has tried to explain everything to Joanna, then she has to answer the phone, why does the camera zoom in on a pair of sunglasses at the far end of the bar?
Answer: They are zooming in on the lighter not the sunglasses. He approaches her to pretend he needs matches in order to overhear who she is speaking with, she notices the lighter and that he didn't need to move from his seat, he already had a way to light his cigarette.
Chosen answer: It's not the sunglasses. It's the matches. Nick is acting as though he is coming closer to Joanna to get a pack of matches, which she then notices he already has. She realises that he is trying to eavesdrop on her conversation, and although she was previously buying his apology her demeanor changes drastically once she is finished with the phone call.