In light of the Murch reading, I wanted to share an application that a past professor/advisor of mine co-developed in order to measure shot length (as well as shot type) while watching movies. It’s called cinemetrics: http://www.cinemetrics.lv/index.php
There’s also a great database of already measured films, so if you search for your favorite film (it’s likely) you can learn about its characteristics from an editor’s perspective: http://www.cinemetrics.lv/database.php
Something fun to consider is the way in which a tool like this changes the movie-watching experience. When I first started watching movies while using the tool, it took quite awhile before I got comfortable using it. Instead of focusing on the movie, I had to focus on both the movie and my using the tool in order to ensure accurate data capture.
p.s., there are 4 entries in the database for the 400 blows.