Clever Camera Tricks
Although ILL was shot in a basic three camera setup, the set designers did much to amplify the opportunity for obtaining tight shots.
For instance, the original wall between the kitchen and the living room was just that - a solid wall without shutters. But Desi and Jess O. realized they could shoot through the open shutters, creating a less claustrophobic look.
In the second apartmement, there was a square board just above the fireplace (usually covered by a vase of flowers). When super tight angles were needed of the opposite side, the board was removed and one of the cameras shot through that vacant square from the bedroom.
Example: when Lucy snuggles up to Ricky in the second scene of "The Camping Trip", she is seated on the sofa and he is seated in the adjoining chair. Ball's closeup is standard, while Desi's is tightly angled from the "bedroom wall."
They didn't utilize this angle often, but when they did so it was effective.
My fave is the set for Caroline's apartment in "Baby Pictures." We see Caroline take the babies in and out of the hallway door. When she returns to the living room, she closes the door. But once the main camera follows her back to the sofa, a stagehand has quietly opened it, so Caroline's closeup camera can get her nasty lines/expressions with a much tighter angle by shooting THROUGH the door.
Dozens of other three camera sitcoms adopted these tricks through the decades (I used to observe these little tricks when I attended several tapings of The Golden Girls).