Picturing characters.

This is my drawing of the K’lenws, a character from the novel I’m working on now. And no, it doesn’t quite look like the image I have in my head, but that’s mostly because of my limited drawing skills.
There’s a great article over at Jacket Mechanical on picturing books, particularly characters in books. Peter Mendelsund argues that although we remember the experience of reading a book as a continuous unfolding of images, in fact the images we hold are very hazy. He even warns that “One should only watch a film adaptation of a favorite book after considering, very carefully, that the casting of the film may very well become the permanent casting of the book in one’s mind.”
I’ve known people to resist seeing a film because the characters won’t look like the people they’ve imagined, but for me, it is more about the overall feel. Will the film capture the mood, the ambience of the book? When I read something I’m engrossed in (and when I write a character I know well) there is certainly something about them, an essence, that I hold in my brain. But is it a complete image? I don’t know that it is. Although I’d know if the image was wrong.
In many ways I think the reader needs to be able to fill in the image for themselves. My daughter, for example, imagined Sckel in What the Dead Said as wearing a hat. No hat was mentioned, but for her a hat was just right.
What do you think? Are the images for the characters you read/write clear or hazy?