I recently got the opportunity to try film acting, and it really made me appreciate the differences between acting onstage and acting for the camera, as well as the advantages to each.
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Since the camera is so close, and able to pick up so much, film acting requires the actor to be completely authentic in their actions, words, and facial expressions . This often means that less equals more on the camera. As well, the camera will pick up on the slightest amount of nervousness, or any tiny habits, such as blinking fast or flaring your nostrils, therefore it is necessary to have complete control over your body.
- Theatre on the other hand, needs a balance between authenticity and exaggerating volume, actions, and your character`s physicality, as you may have audience members sitting very far back in the theatre.
- Performing live on stage allows the actor to pass through and build on their character arc throughout the play because the scenes are happening sequentially, right after the previous ones. You`re not being required to go in and out of character between each scene. I think staying in character for a longer time is easier, because it takes a lot of focus to get into the mindset of your character in the first place.
- When shooting a film, often the scenes aren`t shot in a sequential order. This is often because some locations are only available at certain times. Therefore, an actor probably needs to fully develop their character before starting shooting, and they must be able to fully access any emotion at any time. They might shoot a scene where they`re having a happy phone conversation, then right after, shoot a scene where they`re at a funeral. They need to very quickly get into the mindset of the character in the funeral, in order to fully portray the sadness needed.

- As well, obviously in onstage acting, if you make a mistake, the show has to somehow pick back up and keep on going.
- In film acting, theoretically you could take as many shots as you want until the acting is perfect (there isn`t always time for that, though).
- The camera picks up on the tiniest imperfections.
- Stage acting is more forgiving towards appearances, and the bigger a stage and the farther away an audience, the more makeup and hair products that can be used.
There are of course many more differences, but I believe that the ones that I mentioned are the biggest differences that an actor should know about.