How character description differs in screenplays and novels
One of the first reactions I always have when viewing a film adapted from a novel I’ve read is that the actors portraying the characters are never what I pictured them to be from the descriptions in the novel. Novel writers often spend pages and pages elaborating on the way each major character looks. We learn of their skin color, how smooth it is, the shape and size of their eyes, the abundance or lack of eyelashes, the exact color of their irises and how it varies in different light. We know how long their hair is, how soft, what color it is and how it lights up in the sun. The physical descriptions in novels are long, lengthy, and extremely detailed. Novel writers often create visions of men and women so beautiful that it is impossible for a real human to accurately portray this beauty on screen, and the resulting cast pales in comparison to the gods and goddesses described in the film. While novelists have every right and creative license to create these fantastical visions-whether beautiful or ugly-a screenwriter is limited in the amount and detail he or she should include when describing a character.
While the novelist has all the time in the world to describe the intricacies of what their characters look like, the screenwriter must be brief, and, it is important to limit physical description so that you do not limit casting. For most screenplays, the exact size, shape, and coloring of a character is unimportant. The overall look-young or old, fat or thin, beautiful, ugly, or average-is what matters more than blonde or brunette, blue or brown eyed. There are hundreds of beautiful young actresses, but if you insist that your heroine is five-foot-two, one-hundred and five pounds with long, curly auburn hair and green eyes, you are limiting the casting down to very few women who fit that description. Does it really matter to your story whether a character has blue, gray, brown, or hazel eyes? Probably not. In the rare instances when a certain physical trait is vital to the story, it should be only one thing and you should be flexible with it.
Character description in a screenplay should be brief-in keeping with the style of brevity and clear concise writing that screenwriters must employ. Again, because a screenplay, unlike a novel, is only able to convey what we see and hear, the screenwriter must use the few words allotted to character description to describe not just the looks, but the overall essence of the person. If a screenwriter spends too much time on hair and eye color or how beautiful a character’s body is, there is no space left to describe what the character is like-their real essence, who they are and how they act-the part of them that can be portrayed by a skilled actor of any physical type.
While novelists can spend even more time getting inside their character’s heads and describing how they think and feel at any moment, screenwriters must convey the character’s personality and attitude about life in a few words or sentences in the character description. Novelists can pause the story and get involved in the character’s past, explaining what happened to make them act a certain way. They can reveal a character’s thoughts and how that character approaches life, their views on the world. They can take as long as necessary to explain this, and they can insert more revelations whenever they want during the story, because in a novel it is acceptable to interrupt the forward momentum of the plot with backstory, thoughts, and a characters feelings or inner monologue. A screenwriter must give this sense of what the character is like when they are introduced, by providing visual clues-the way the character dresses, the way they look, their facial expressions. The way they stand, walk, or speak. These visual details, when explained by a skilled screenwriter, can convey as much or more than pages of introspection written by a novelist, but the screenwriter must carefully choose the correct, vivid visual details that most effectively convey who their character really is, without the luxury of actually getting inside their head.

Yet another interesting entry, keep em coming!