It's a tough question, not just for viewers, but for directors too. These days, they have tons of aspect ratios to choose from. How do they pick them? Which is appropriate? Here's looking at different aspect ratios from different films. Watch it below:

Here are the flims in the clip:

Family Guy S08 E10 "Big Man on Hippocampus"
Citizen Kane (1941)
Wizard of Oz (1939)
Batman: The Dark Knight (2008)
500 Days of Summer (2009)
Scott Pilgrim Vs. The World (2010)
Pee Wee Herman's Big Adventure (1985)
The Grand Budapest Hotel (2014)
Django Unchained (2009)
Aunty Donna "This is What You Get"
Napoleon Dynamite (2005)
Star Wars: The Force Awakens (1977)
Interstellar (2014)
Apollo 13 (1995)
Galaxy Quest (1999)
The Dark Knight Rises (2012)
The Hunger Games (2012)
Chronicle (2012)
The Incredibles (2004)
Catch Me If You Can (2002)
Life of Pi (2012)
Oz The Great and Powerful (2013)
Ben-Hur (1959)
The Big Lebowski (1998)

Watch the video: