For comparing the adaptations of a particular work to each other, or comparing a work's adaptations to the source work.
Due to the differences in the media's methods, production, audiences and other details, there are often significant differences between:
- movies based on a book and the book itself
- TV shows based on a comic series and the comics themselves
- different movie adaptations of the same written work
- the novelisation of a movie and the movie itself
The differences can be minor (some small plot condensing to fit a larger book into a 2-hour movie, or adding dialog to express some exposition text; to a dramatic re-work which leaves nothing in common between two works aside from the title and main character's name, to completely perverting the book's ideas and message).
Harry Potter's eyes were - importantly - green in the books (same as Lily), whereas the movies turned them into non-green because of logistical problem with contacts
Elves appearing at Helm's Deep in the Lord of the Rings movie (and the removal of the Shire plot from Book 3, which is a lot more of a change), along with compressing Arwen and Glorfindel into the single action heroine.
The Starship Troopers novel by Heinlein was remade by Verhoeven into a 100% opposite movie which had almost nothing in common with the book aside from the title and some trappings and character names (the book's fully democratic society which has franchise limitations requiring all voters to be those who volunteered for a dangerous service to the Federation, including but not limited to the military, with tons of philosophical excursions into theory of politics; was turned into a campy fascist-like militarist caricature).
This tag is for questions asking about details around such differences in an objective way.