I’ve managed to make myself so sensitive to this that I get all tense when there’s a multi-camera setup for a conversation, waiting for the moment when they cut from A to B and someone’s hands or head have teleported to a slightly (and sometimes not slightly!) different position.
Very few such sequences complete without my noticing some spot where shots don’t match up.
Another one is key lights reflected in eyeballs. Nearly ruins Jackson’s LOTR trilogy for me, it’s in basically every damn scene. In several shots you can practically diagram out their whole lighting rig from a the reflections on an actor’s eye, so many lights are plainly and distinctly visible. You see it some in lots of movies but OMG it’s bad in those.
I have always considered it an actors job to ensure their hands or cigarette or whatever are in the same position when they hit the same word during multiple takes.
It's never going to be perfect or identical. Actors' #1 job is to give an emotionally believable, powerful performance. A thousand little details are different in every take, and your movements will change to reflect what is authentic in the moment. In fact, editors want emotional variety so that they have more options in assembling the scene.
Yes, things are blocked ahead of time. You'll stand up at the same moment, you'll stop walking at a particular mark. But there are limits, especially with things like hands and cigarettes. If you look for continuity errors around those, you'll find them everywhere. Actors, directors and editors have more important things to worry about.
Very few such sequences complete without my noticing some spot where shots don’t match up.
Another one is key lights reflected in eyeballs. Nearly ruins Jackson’s LOTR trilogy for me, it’s in basically every damn scene. In several shots you can practically diagram out their whole lighting rig from a the reflections on an actor’s eye, so many lights are plainly and distinctly visible. You see it some in lots of movies but OMG it’s bad in those.