20Kristen Stewart's Computer-Assisted Eye Color
Sometimes, more minor physical details about a book character are glossed over or changed when said character is adapted to movie form. Things like hair and eye color, for instance, are often seen as easy to alter when selecting an actor-- but other times, everything has to be just
right. Such was the case when the naturally green-eyed Kristen Stewart took on the role of brown-eyed Bella Swan, as she wore contacts to make her eyes brown-- at least in her pre-vampiric state.
That said, colored contact lenses can cause a lot of issues. An example of this occurred during Bella and Jacob's sad scene in the rain during New Moon, with the rain irritating Stewart's contacts to the point that she couldn't wear them. For that scene, her eyes had to be re-colored in post-production, which is costly and time-consuming.