We all know that translating a book to a film is not the easiest of tasks. Not only do you have to contend with the author, who may rankle at his or her work being changed in even the slightest way, you also have to deal with those who loved the book and, similarly to the writer, find any changes heretical. Nobody wants to incur the wrath of those that will potentially come and watch the adaptation, but sometimes changing things is necessary, especially when complicated sub-plots vie for attention.

Certainly, those at HPLexicon.org believes that in order for a book to translate properly, changes are extremely important. However, says the site, "for fans these differences can be painful indeed. What many fans consider to be key scenes in the books are sometimes marginalized or completely ignored in the film."

As the release date for seventh and final book Harry Potter and the Deathly Hallows draws ever closer, and fifth film Harry Potter and the Order of the Phoenix is released in cinemas worldwide, Digital Spy takes a look at the main changes involved in the translation of each book to film thus far.

Harry Potter and the Philosopher's Stone

Things that were cut

We don't really see the Muggle point of view at the start of the film - Dudley's sidekick Piers Polkiss fails to appear at all.

Large cuts are made to material detailing the attempted escape from Privet Drive after Harry's Hogwarts letters start arriving thick and fast, and we miss an entire month of Harry's summer preceding his arrival at Hogwarts.

Sadly, the Sorting Hat's song is also cut, as is Harry and Draco's first exchange, with their original meeting in Madam Malkin's robe shop changed wholly and their first duel cut, and while some points may be insignificant, to understand the enmity that grows between Harry and Draco in years to come fully, it would have been nice to leave it in for purposes of accuracy.

Although the whole point of the film concerns the Philosopher's Stone, we barely get a look at creator Nicolas Flamel, whose role is dramatically chopped and changed around, only for some of it to appear on DVD extras.

Such academic moments as Hermione's potion riddle on the way to Harry's confrontation with Quirrell obviously did not translate as well to screen as Ron and his chess playing, but even so, it is somewhat disappointing that it was cut.

Plotlines that were changed

With the changing about of Harry and Draco's first meeting, we see little of Scabbers, the rat who later turns out to be Peter Pettigrew. Although these moments may seem inconsequential, JK Rowling is well known for putting in clues throughout her books to guide those who happen upon them, something the films cannot replicate.

Alterations are rife throughout, with Norbert the dragon's removal being done by Dumbledore rather than the original, rather complicated plot strand where Harry and Hermione attempt to help Hagrid out with his little 'problem'. This differentiation necessitated other plot changes, with characters being switched around and detentions in the Forbidden Forest never occurring.

One of the most peculiar moments is the depiction of Dudley and Aunt Petunia as blonde - with Dudley particular described as such, being made out to look rather piggish, but suddenly, in the films, they are brunette. Certainly this is a petty thought, but one that angered hardcore fans. This colour change is a disease that affects Firenze too, who is described in the book as palomino with light blonde hair, but again is dark in the film. Who knows what Chris Columbus was thinking when he cast these roles!