Downey Jr. said:
“When you do the Hud work, usually it’s kind of the last thing in the schedule and you’re going back and essentially living the movie again in close-up, tired.”
These types of scenes can be particularly difficult because the actor is isolated from the rest of the cast and left to interact with nothing but a green screen.
He did mention one of the perks of these kinds of shots however:
“We had the luxury of being efficient enough to sometimes say, ‘Stop, stop. Wait a second. Let’s not just shoot these next 20 lines. Let’s look at the scene and how can we make it a little better or different.’”
Marvel Studios’ “Iron Man 3″ pits brash-but-brilliant industrialist Tony Stark