One thing we should not overlook: Fox News (reportedly by random choice) got the exclusive rights to the "primary video feed" for the Democratic Convention.
That means that, no matter what channel you see video footage on, it is the footage that Fox - in their infinite and oh-so-fair-and-unbalanced judgment - deigned to shoot and make available in the first place.
That means that when you see a bizarre-looking or ugly or bored-looking or frowning person on camera while Barack or Michelle or Nancy P or Hillary C or Joe Biden or whoever is speaking, it was Fox News that chose to capture that image instead of any of the other possible camera shots.

Methinks I've already seen a few choice examples of this "selective camera usage" tonight.

G